Grade Level

Hydrogen Bromide

Sunday October 31, 2010

WARNING!! THIS EXPERIMENT IS PARTICULARLY DANGEROUS!! (No kidding.) This experiment is for advanced students.

We’ve created a video that shows you how to safely do this experiment, although if you’re nervous about doing this one, just watch the video and skip the actual experiment.

Bromine is a particularly nasty chemical, so be sure to very carefully follow the steps we’ve outlined in the video. You MUST do this experiment outdoors. We’ll be making a tiny amount to show how the chemical reactions involving bromine work.

[am4show have=’p9;p52;p91;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Isn’t it interesting how many ways we can use the same techniques and, by just changing a few chemicals, we can learn about so many different chemical reactions? This lab is similar in technique to the Generating Hydrochloric Acid lab. Using the same techniques, we will produce hydrogen bromide.

Hydrogen bromide (HBr) was used as a sedative in the late 1800s and early 1900s. Once they found out how poisonous it really was (after enough people became blind and/or dead), someone had the wonderful idea that maybe we shouldn’t use it anymore. It was also used to control epilepsy until the substitute Phenobarbital came on the scene in 1911. HBr is still used to treat epilepsy in dogs. In cats HBr causes inflammation of the lungs and makes for a very unhappy cat.

Materials:

Alcohol burner
Lighter
Wire screen
Tripod stand
Glass jar
Rubber tubing
900 Glass tubing
One-hole rubber stopper
Chemistry stand
Test tube holder
Test tube
Potassium bromide (KBr) (MSDS)
Sodium hydrogen sulfate (NaHSO₄) (MSDS) Sodium hydrogen sulfate is very toxic. Respect it, handle it carefully and responsibly. Do not take it for granted.
Burette
Water
Sodium carbonate (Na₂CO₃) (MSDS)
Silver nitrate (AgNO₃) (MSDS)

NOTE: Be very careful when handling the sodium hydrogen sulfate – it’s highly corrosive and dangerous when wet. Handle this chemical only with gloves, and be sure to read over the MSDS before using.

Maintain good and proper lab techniques. We are working with some nasty stuff in this lab. We need to perform this lab outdoors if possible, or indoors with lots of ventilation. The reaction advances in stages:

Bubbles in the burette tell us the reaction is occurring.
Brown streaks will appear in the water contained in the glass jar as gas collects there.
Brown vapor will begin to appear in the test tube. When the reaction is complete, the test tube will contain lots of brown vapor.

After we produce HBr, we will perform a number of tests to see if it is an acid or a base.

Test contents of test tube with blue litmus paper. Red color change indicates an acid.
Add baking soda to the HBr. Bubbles and the solution turning white. HBr is an acid in this test because it is obviously reacting with a base.
If a magnesium strip placed in the HBr corrodes, or starts to dissolve, then HBr is an acid.
With the addition of silver nitrate to the HBr, if a white cloudiness occurs and crystals form in the bottom of the test tube, then HBr is an acid.

C3000: Experiments 134-138

Download Student Worksheet & Exercises

Here’s what’s going on in this experiment:

KBr + NaHSO₄ –> HBr + KNaSO₄

Potassium bromide and sodium hydrogen sulfate, when heated, produce hydrogen bromide and potassium sodium sulfate.

Cleanup: We are going to clean everything thoroughly after we finish the lab. After cleaning with soap and water, rinse thoroughly. Chemists use the rule of “three” in cleaning glassware and tools. After washing, chemists rinse out all visible soap and then rinse three times more.

Storage: Place cleaned tools and glassware in their respective storage places.

Disposal: Liquids can be washed down the drain. Solids are thrown in the trash.

[/am4show]

Hydrogen Chlorine Gas

Sunday October 31, 2010

WARNING!! THIS EXPERIMENT IS PARTICULARLY DANGEROUS!! (No kidding.) This experiment is for advanced students.

We’ve created a video that shows you how to safely do this experiment, although if you’re nervous about doing this one, just watch the video and skip the actual experiment.

The gas you generate with this experiment is lethal in large doses, so you MUST do this experiment outdoors. We’ll be making a tiny amount to show how the chemical reactions of chlorine and hydrogen work.

[am4show have=’p9;p52;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Hydrochloric acid is a strong acid. It is highly corrosive, which means that this acid will destroy or irreversibly damage another substance it comes in contact with. Simple terms….it is pretty nasty, so take special care when working with or around it.

HCl is used in processing leather, cleaning products, and in the food industry. We are most familiar with HCl in the form of Gastric Acid. HCl is in gastric acid and is one of the main ingredients in our stomach to aid in digestion of our food. In our lab we will produce hydrogen chlorine gas and add water to turn change it into hydrochloric acid.

Materials:

Glass jar
90⁰ bend glass tubing
One-hole rubber stopper
Chemistry stand
Wire mesh
2 Test tubes
Test tube clamp
Alcohol burner
Lighter
Tripod stand
Sodium hydrogen sulfate (MSDS) Sodium hydrogen sulfate is very toxic. Respect it, handle it carefully and responsibly. Do not take it for granted.
Salt
One-hole cork
Medicine dropper
Water
Solid rubber stopper

Perform this experiment outdoors. If that is not a possibility, and you must do it inside, open doors and windows to provide lots of ventilation. Hydrogen chlorine gas inhalation can be fatal, but we are only producing a very small amount.

There are many steps in this lab, so go slow and steady. Read the lab over several times so you are sure what is going on and what is happening next.

When we shake the sodium hydrogen sulfate and the salt together in a stoppered test tube, we are trying to produce a heterogeneous mixture. Heterogeneous is a scientific word that means substance are mixed all together to be as one. A sample taken from one spot in the mixture should be the same as a sample taken from any other spot in the mixture.

At some point in this lab, we need to point the test tube containing the reaction slightly down. This is so the hydrogen chlorine gas can flow downhill. The gas is denser than air, so it will sink to the bottom of anything air filled…..like a room or a test tube.

Hydrogen chloride gas is poisonous – DO NOT INHALE!

When the medicine dropper / cork tool is placed in the water, water will be sucked up into the test tube. The water combines with the hydrogen chlorine gas to create hydrochloric acid.

A double replacement chemical reaction will take place in this experiment. A free hydrogen ion (+) and a free sodium ion (+) will be produced. Because their charges are alike, they cannot bond, but they can take each other’s place. The spots they each left are negatively charged after the hydrogen and sodium have departed. Opposites attract, and they reorganize into a double replacement reaction.

C3000: Experiment 112

Download Student Worksheet & Exercises

Here’s what’s going on in this experiment:

NaCl + NaHSO₄–> HCl + Na₂SO₄

Salt is combined with sodium hydrogen sulfate and heated to produce hydrochloric acid and sodium sulfate

Storage: Place cleaned tools and glassware in their respective storage places.

Disposal: Our HCl needs to be neutralized before disposal. Put a bit of baking soda into the test tube. The contents should bubble as the neutralization is taking place. After neutralization, the liquid is safe, and can be washed down the drain. Solids are thrown in the trash.

[/am4show]

Fire-Water Balloon

Sunday September 5, 2010

If you’ve ever had a shot, you know how cold your arm feels when the nurse swipes it with a pad of alcohol. What happened there? Well, alcohol is a liquid with a fairly low boiling point. In other words, it goes from liquid to gas at a fairly low temperature. The heat from your body is more then enough to make the alcohol evaporate.

As the alcohol went from liquid to gas it sucked heat out of your body. For things to evaporate, they must suck in heat from their surroundings to change state. As the alcohol evaporated you felt cold where the alcohol was. This is because the alcohol was sucking the heat energy out of that part of your body (heat was being transferred by conduction) and causing that part of your body to decrease in temperature.

As things condense (go from gas to liquid state) the opposite happens. Things release heat as they change to a liquid state. The water gas that condenses on your mirror actually increases the temperature of that mirror. This is why steam can be quite dangerous. Not only is it hot to begin with, but if it condenses on your skin it releases even more heat which can give you severe burns. Objects absorb heat when they melt and evaporate/boil. Objects release heat when they freeze and condense.

Do you remember when I said that heat and temperature are two different things? Heat is energy – it is thermal energy. It can be transferred from one object to another by conduction, convection, and radiation. We’re now going to explore heat capacity and specific heat. Here’s what you do:

[am4show have=’p8;p9;p23;p50;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]

You Need:

Balloon
Water
Matches, candle, and adult help
Sink

Download Student Worksheet & Exercises

1. Put the balloon under the faucet and fill the balloon with some water.

2. Now blow up the balloon and tie it, leaving the water in the balloon. You should have an inflated balloon with a tablespoon or two of water at the bottom of it.

3. Carefully light the match or candle and hold it under the part of the balloon where there is water.

4. Feel free to hold it there for a couple of seconds. You might want to do this over a sink or outside just in case!

So why didn’t the balloon pop? The water absorbed the heat! The water actually absorbed the heat coming from the match so that the rubber of the balloon couldn’t heat up enough to melt and pop the balloon. Water is very good at absorbing heat without increasing in temperature which is why it is used in car radiators and nuclear power plants. Whenever someone wants to keep something from getting too hot, they will often use water to absorb the heat.

Think of a dry sponge. Now imagine putting that sponge under a slowly running faucet. The sponge would continue to fill with water until it reached a certain point and then water started to drip from it. You could say that the sponge had a water capacity. It could hold so much water before it couldn’t hold any more and the water started dripping out. Heat capacity is similar. Heat capacity is how much heat an object can absorb before it increases in temperature. This is also referred to as specific heat. Specific heat is how much heat energy a mass of a material must absorb before it increases 1°C.

Exercises Answer the questions below:

What is specific heat?
1. The specific amount of heat any object can hold
2. The amount of energy required to raise the temperature of an object by 1 degree Celsius.
3. The type of heat energy an object emits
4. The speed of a compound’s molecules at room temperature
Name three ways thermal energy can be transferred from one object to another:
At what point does the balloon pop?
True or False: Water is poor at absorbing heat energy.
1. True
2. False

[/am4show]

Convection Currents

Sunday September 5, 2010

Every time I’m served a hot bowl of soup or a cup of coffee with cream I love to sit and watch the convection currents. You may look a little silly staring at your soup but give it a try sometime!

Convection is a little more difficult to understand than conduction. Heat is transferred by convection by moving currents of a gas or a liquid. Hot air rises and cold air sinks. It turns out, that hot liquid rises and cold liquid sinks as well.

Room heaters generally work by convection. The heater heats up the air next to it which makes the air rise. As the air rises it pulls more air in to take its place which then heats up that air and makes it rise as well. As the air get close to the ceiling it may cool. The cooler air sinks to the ground and gets pulled back near the heat source. There it heats up again and rises back up.

This movement of heating and cooling air is convection and it can eventually heat an entire room or a pot of soup. This experiment should allow you to see convection currents.

[am4show have=’p8;p9;p23;p50;p82;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

You need:

A pot
A stove with adult help
Pepper
Ice cubes
Food Coloring (optional)

1. Fill the pot about half way with water.

2. Put about a teaspoon of pepper into the water.

3. Put the pot on the stove and turn on the stove (be careful please).

4. Watch as the water increases in temperature. You should see the pepper moving. The pepper is moving due to the convection currents. If you look carefully you many notice pepper rising and falling.

5. Put an ice cube into the water and see what happens. You should see the pepper at the top of the water move towards the ice cube and then sink to the bottom of the pot as it is carried by the convection currents.

6. Just for fun, put another ice cube into the water, but this time drop a bit of food coloring on the ice cube. You should see the food coloring sink quickly to the bottom and spread out as it is carried by the convection currents.

Did you see the convection currents? Hot water rising in some areas of the pot and cold water sinking in other areas of the pot carried the pepper and food coloring throughout the pot. This rising and sinking transferred heat through all the water causing the water in the pot to increase in temperature.

Heat was transferred from the flame of the stove to the water by convection. More accurately, heat was transferred from the flame of the stove to the metal of the pot by conduction and then from the metal of the pot throughout the water through convection.

[/am4show]

Sensing Temperature

Sunday September 5, 2010

Temperature is a way of talking about, measuring, and comparing the thermal energy of objects.

[am4show have=’p8;p9;p23;p50;p151;p152;p71;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

The words “hot” , “cold”, “warm” and so forth describe what scientists call thermal energy. Thermal energy is how much the molecules are moving inside an object. The faster molecules move, the more thermal energy it has.

Objects that have molecules moving very quickly are said to have high thermal energy or high temperature. Like a cloud of steam, for example. The higher the temperature, the faster the molecules are moving inside that steam cloud.

Temperature is just a speedometer for molecules. The speed of the molecules in ice cream is way slower than it is in a hot shower.

If everything is made of molecules, and these molecules are speeding up and slowing down, what do you think happens if they change speed a lot? Do you think my kitchen table will start vibrating across the room if the table somehow gets too hot?

No, probably not, my table will not start jumping around the room, no matter how hot it gets. It would melt down into a mush first! But some interesting things do happen when molecules change speeds.

There are three common states of matter – I bet you know what they are already: solid, liquid, and gas. Water is really special because it can a solid, liquid or gas state pretty normal temperatures. You don’t need a mad scientist lab to get it to go into any of these three states.

Water is one of the only substances that expands instead of shrinks when it freezes. It’s also a polar molecule, meaning that if you stick a static charge next to it, like a balloon you rubbed on your head, you can get the water to move.

Imagine an icicle. The water is in a solid state when it’s an icicle. It’s holding its shape. The molecules in the water are held together by strong, stiff bonds. These bonds hold the water molecules in a tight pattern called a matrix. This matrix holds the water molecules in a crystalline pattern.

Can you imagine breaking off an icicle and sticking it in a tea kettle on the stove? Now, let’s pretend to turn on the heat. The heat is transferred from the stove to the kettle to the icicle.

What happens to our icicle?

As the icicle absorbs the heat, the molecules begin to vibrate faster (the temperature is increasing). When the molecules vibrate at a certain speed (they gain enough thermal energy) they stretch those strong, stiff matrix crystalline bonds enough that the bonds become more like rubber bands or springs and they stretch and get all loose-goosey.

That’s when the icicle becomes liquid. There are still bonds between the molecules, but they are a bit loose, allowing the molecules to move and flow around each other.

The act of changing from a solid to a liquid is called melting. The temperature at which a substance changes from a solid to a liquid is called its melting point. For water, that point is 32° F or 0° C. (Remember those numbers from the slide with all the temperature scales?)

Now if we continue heating, we see our icicle go from solid to completely liquid, and now we notice bubbling. What’s going on now?

Now the temperature is at 212° F or 100° C and the water is going from a liquid state to a gaseous state. This means that the loosey goosey bonds that connected the molecules before have been stretched as far as they go, can’t hold on any longer and “POW!” they snap.

Those water molecules no longer have any bonds and are free to roam aimlessly around the room (think toddlers). Gas molecules move at very quick speeds as they bounce, jiggle, crash and zip around any container they are in (kind of like toddles on sugar). The act of changing from a liquid to a gas is called evaporation or boiling and the temperature at which a substance changes from a liquid to a gas is called its boiling point.

Now if we turn off the stove, what do you think happens?

Our gaseous water molecules get close to something cool, they will combine and turn from gaseous to liquid state. This is what happens to your bathroom mirror during a shower or bath. The gaseous water molecules that are having fun bouncing and jiggling around the bathroom get close to the mirror. The mirror is colder than the air. As the gas molecules get close they slow down due to loss of temperature. If they slow enough, they form loosey goosey bonds with other gas molecules and change from gas to liquid state.

The act of changing from gas to liquid is called condensation. The temperature at which molecules change from a gas to a liquid is called the condensation point. Clouds are made of hundreds of billions of tiny little droplets of liquid water that have condensed onto particles of some sort of dust.

Now let’s turn the heat down a bit more and see what happens. Imagine we stick the tea kettle in the freezer. As the temperature drops and the molecules continue to slow, the bonds between the molecules can pull them together tighter and tighter.

Eventually the molecules will fall into a matrix, a pattern, and stick together quite tightly. This would be the solid state. The act of changing from a liquid to a solid is called freezing and the temperature at which it changes is called (say it with me now) freezing point.

Think about this for a second – is the freezing point and melting point of an object at the same temperature? Does something go from solid to liquid or from liquid to solid at the same temperature?

If you said yes, you’re right!

The freezing point of water and the melting point of water are both 32° F or 0° C. The temperature is the same. It just depends on whether it is getting hotter or colder as to whether the water is freezing or melting.

The boiling and condensation point is also the same point.

Crazy Temperatures

Here’s an experiment you can do to baffle your senses: Fill one glass with hot water (not boiling), another with ice water, and a third with room temperature water. Place a finger in the hot water and a finger in the ice cold water for a minute or two. Then stick both fingers in the room temperature cup.

How does that feel?

Did it seem that each finger detected a different temperature when placed in the room temperature cup? Weird! So what gives?

Materials:

3 cups of water (see video)
your hands

Download Student Worksheet & Exercises

Your skin contains temperature sensors that work by detecting the direction heat flow (in or out of your body), not temperature directly. These sensors change temperature depending on their surroundings. So when you heated up one finger, and then placed it in cooler water, the heat flowed out of your body, telling your brain it was getting cooler. The ice water finger was detecting a heat flow into your body… and presto! You have one confused brain.

In order for heat to flow, you need to have a temperature difference. Did you notice how your fingers weren’t good thermometers with this experiment? This is why scientists had to invent the thermometer, because the human body isn’t designed to detect temperature, only heat flow.

[/am4show]

Balloon Gymnastics

Sunday September 5, 2010

Is it warmer upstairs or downstairs? If you’re thinking warm air rises, then it’s got to be upstairs, right? If you’ve ever stood on a ladder inside your house and compared it to the temperature under the table, you’ve probably felt a difference.

So why is it cold on the mountain and warm in the valley? Leave it to a science teacher to throw in a wrench just when you think you’ve got it figured out. Let’s take a look at whether hot air or cold air takes up more space. Here’s what you do:

[am4show have=’p8;p9;p23;p50;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

water
plastic bottle
balloon
stove top and saucepan or the setup in the video

Download Student Worksheet & Exercises

1. Pour a couple of inches of water into an empty soda bottle and cap with a 7-9″ balloon. You can secure the balloon to the bottle mouth with a strip of tape if you want, but it usually seals tight with just the balloon itself.

2. Fill a saucepan with an inch or two of water, and add your bottle. Heat the saucepan over the stove with adult help, keeping a close eye on it. Turn off the heat when your balloon starts to inflate. Since water has a high heat capacity, the water will heat before the bottle melts. (Don’t believe me? Try the Fire-Water Balloon Experiment first to see how water conducts heat away from the bottle!)

3. When you’re finished, stick the whole thing in the freezer for an hour. What happened to the balloon?

What’s going on? So now what do you think? Does the same chunk of air take up more or less space when it’s hot? Cold? When you heat air, it expands because the air molecules move around a lot more when you add energy. The molecules zip around and wiggle like crazy, bouncing off each other more often than when they are cooler.

Getting back to our original question, the upstairs in a house is warmer because the pockets of warm air rise because they are less dense than cool air. The more the molecules move around, the more room they need, and the further they get spaced out. Think of a swimming pool and a piece of aluminum foil. If you place a sheet of foil in the pool, it floats. If you take the foil and crumple it up, it sinks. The more compactly you squish the molecules together, the more dense it becomes. You can read more about density in Unit 3.

As for why mountains and valleys are opposite, it has to do with the Earth being a big massive ball of warm rock which heats up the lower atmosphere in addition to winds blowing on mountains and changes in pressure as you gain altitude… in a nutshell, it’s complicated! What’s important to remember is that the Earth system is a lot bigger than our bottle-saucepan experiment, and can’t be represented in this way.

Exercises

Draw a group of molecules at a very cold temperature in the space below. Use circles to represent each molecule.
True or False: A molecule that heats up will move faster.
1. True
2. False
True or False: A material will be less dense at lower temperatures.
1. True
2. False

[/am4show]

Homemade Thermostat

Sunday September 5, 2010

If you can remember thermostats before they went ‘digital’, then you may know about bi-metallic strips – a piece of material made from of two strips of different metals which expand at different rates as they are heated (usually steel and copper). The result is that the flat strip bends one way if heated, and in the opposite direction if cooled.

Normally, it takes serious skill and a red-hot torch to stick two different metals together, but here’s a homemade version of this concept that your kids can make using your freezer. Here what you do:

[am4show have=’p8;p9;p23;p50;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

foil wrapper from a stick of gum or candy bar
index card
scissors
tape

Since gum wrappers are paper on one side and foil on the other, you can use one to make your own bi-metallic strip. Flatten out the wrapper into a sheet and find a way fasten the wrapper so it sits upright on an index card (we used the bubble gum itself as the adhesive). Stick it in the freezer overnight and check it in the morning! Where can you place it to flex the other direction?

How does that work? A bimetallic strip is a stack of two metals stuck together. The metal with the higher expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The bi-metallic strip was invented by the eighteenth century clockmaker John Harrison to compensate for temperature-induced changes his clock springs.

[/am4show]

Ghost Coin

Sunday September 5, 2010

This spooky idea takes almost no time, requires a dime and a bottle, and has the potential for creating quite a stir in your next magic show. The idea is basically this: when you place a coin on a bottle, it starts dancing around. But there’s more to this trick than meets the scientist’s eye.

Here’s how you do it:

[am4show have=’p8;p9;p23;p50;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:

coin
freezer
plastic bottle (NOT glass)

Download Student Worksheet & Exercises

Remove the cap of an empty plastic water or soda bottle and replace it with a dime and stick the whole things upright in the freezer overnight. First thing in the morning, take it out and set it on the table. What happens?

Attention: Magicians

If you’re a budding magician, here’s how to modify this experiment to use in your next show. Get a glass container of soda and stick it in the coldest part of your fridge overnight. I know they are getting harder to find these days, but the glass will keep its temperature longer than plastic and enable you to do this trick. In a pinch, you can refill a cleaned glass bottle from a previous use if you can’t locate a fresh glass soda bottle.

As soon as you’re ready to do your trick (practice first!), take it out of the fridge (have it in an ice chest if you’re on stage) and chug the whole thing. (You can ask your audience for help on this – you just want an empty cold bottle for the next part.)

When the bottle is empty but still cold, cap it with a wet dime. Place both hands on the bottle while you “wax eloquent” (make up an engaging story, like “North Winds, come have a taste of soda…”) but be sure to keep your hands on the bottle to warm it up. In about 20 seconds or so, the dime will click up and down, dancing around mysteriously. Keep your hands on the bottle for another 20 seconds or so, and then set it gently on the table with it still dancing, and you’ll find it dancing right on without your hands being there.

How does that work? Was the bottle really empty when you placed it in the freezer? Actually, no… it had air inside of it. The air in the bottle shrank down a bit as it cooled, allowing more air to go into the bottle. When you remove the bottle from the freezer and cap it with the coin, you now have a bottle with more air in it than you started. The air warms and expands, pushing the excess air out the top, making the coin dance. Learn more about air with this Air Expands experiment.

Variations to try:

Is a plastic bottle or glass bottle better for this experiment?
What if you get the coin wet first?
Does a cold or warm coin work better?
What about a penny? Quarter?
Does the size of the bottle matter?

Exercises

When a gas turns into a liquid, this is called:
1. Convection
2. Conduction
3. Absorption
4. Condensation
When water boils, what happens to the bonds between its molecules?
What is the best way to describe how the bonds between water molecules behave when in a liquid state?
1. Solid bridges
2. Rubber bands
3. No bonds
4. Brittle like chalk
The crystalline shape of a solid is referred to as:
1. a matrix
2. a vortex
3. a crystal
4. a cube

[/am4show]

Solar Drinking Bird

Sunday September 5, 2010

The Drinking Bird is a classic science toy that dips its head up and down into a glass of water. It’s filled with a liquid called methylene chloride, and the head is covered with red felt that gets wet when it drinks. But how does it work? Is it perpetual motion?

Let’s take a look at what’s going on with the bird, why it works, and how we’re going to modify it so it can run on its own without using any water at all!

[am4show have=’p8;p9;p23;p50;p85;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]

The bird needs a temperature difference between the head and tail. Since water needs heat in order to evaporate, the head cools as the water evaporates. This temperature decrease lowers the pressure inside the head, pushing liquid up the inner tube. With more liquid (weight in the head), the bird tips over. The bird wets its own head to start this cycle again.

The trick to making this work is that when the bird is tipped over, the vapor from the bottom moves up the tube to equalize the pressure in both sides, or he’d stay put with his head in the cup. Sadly, this isn’t perpetual motion because as soon as you take away the water, the cycle stops. It also stops if you enclose the bird in a jar so water can longer evaporate after awhile. Do you think this bird can work in a rainstorm? In Antarctica?

What’s so special about the liquid? Methylene chloride is made of carbon, hydrogen, and chlorine atoms. It’s barely liquid at room temperature, having a boiling point of 103.5° F, so it evaporates quite easily. It does have a high vapor pressure (6.7 psi), meaning that the molecules on the liquid surface leave (evaporate) and raise the pressure until the amount of molecules evaporating is equal to the amount being shoved back in the liquid (condensed) by its own pressure. (For comparison, water’s vapor pressure is only 0.4 psi).

Note that the vapor pressure will change with temperature changes. The vapor pressure goes up when the temperature goes up. Since the wet head is cooler than the tail, the vapor pressure at the top is less than at the bottom, which pushes the liquid up the tube.

It really does matter whether the bird is operating in Arizona or the Amazon. The bird will dip more times per minute in a desert than a rain forest!

Let’s find out how to modify the bird so it’s entirely solar-powered… meaning that you don’t have to remember to keep the cup filled with water. Here’s what you need:

drinking bird
silver or white spray paint
black spray paint
razor
mug of hot water
sunlight or incandescent light

Download Student Worksheet & Exercises

In this modification, you completely eliminated the water and converted the bird to solar, using the heat of the sun to power the bird. Now your bird bobs as long as you have sunlight!

How does that work? Since the bottom of the bird is now black, and black absorbs more energy and heats up the tail of the bird. Since the tail section is warmer, the pressure goes up and the liquid gets pushed up the tube. By covering the head with white (or silver) paint, you are reflecting most of the energy so it remains cool. Remember that white surfaces act like mirrors to IR light (which is what heat energy is).

Questions to Ask: Does it work better with hot or cold water? Does it work in an enclosed space, such as an inverted aquarium? On a rainy day or dry? In the fridge or heating pad?

Exercises Answer the questions below:

Where does most of the energy on earth come from?
1. Underground
2. The sun
3. The oceans
What is one way that we use energy from the sun?
What is the process by which the liquid is being heated inside the bird?
1. Precipitation
2. Pressure
3. Evaporation
4. Transpiration

[/am4show]

Hero Engine

Sunday September 5, 2010

There are lots of different kids of heat engines, from stirling engines to big jet turbines to the engine in your car. They all use clever ways to convert a temperature difference into motion.

Remember that the molecules in steam move around a lot faster than in an ice cube. So when we stick hot steam in a container, we can blow off the lid (used with pistons in a steam engine). or we can put a fan blade in hot steam, and since the molecules move around a lot, they start bouncing off the blade and cause it to rotate (as in a turbine). Or we can seal up hot steam in a container and punch a tiny hole out one end (to get a rocket).

One of the first heat engines was dreamed up by Hero of Alexandria called the aeolipile. The steam is enclosed in a vessel and allowed to jet out two (or more) pipes. Although we’re not sure if his invention ever made it off the drawing board, we do know how to make one for pure educational (and entertainment) purposes. Are you ready to have fun?

THIS EXPERIMENT USES FIRE AND STEAM…GET ADULT HELP BEFORE YOU OPERATE THE ENGINE.

Here’s what you do:

[am4show have=’p8;p9;p23;p50;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:

soda can
fishing line
razor
stand
drill or large nail and hammer
adult help
candle

IMPORTANT NOTE: As the water boils, your can will spin. The hot steam shoots out the sides, so take care not to get burned. As the can spins, it may wobble and shake, especially if it’s off-center. Be careful not to get shot with boiling water!!

What’s going on? When the water boils, the molecules inside are turning into hot steam and moving very quickly, bouncing off the can and out the pipes. Rockets and balloons use this same principle – the pressurized air shoots out the open end and the balloon (or rocket) moves in the opposite direct. Newton’s third law in motion! The two jets at an angle work together to spin the can.

Do you think the size of the hole matters?
Does it matter how many candles you use?
What if you used four holes instead of two? Six? Twenty?
Are beer cans better?

[/am4show]

Food Dye Currents

Sunday September 5, 2010

When something feels hot to you, the molecules in that something are moving very fast. When something feels cool to you, the molecules in that object aren’t moving quite so fast. Believe it or not, your body perceives how fast molecules are moving by how hot or cold something feels. Your body has a variety of antennae to detect energy. Your eyes perceive certain frequencies of electromagnetic waves as light. Your ears perceive certain frequencies of longitudinal waves as sound. Your skin, mouth and tongue can perceive thermal energy as hot or cold. What a magnificent energy sensing instrument you are!

Let’s find out how to watch the hot and cold currents in water. Here’s what you need to do:

[am4show have=’p8;p9;p23;p50;p82;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

two bottles of water
food coloring
bathtub or sink
index card or business card

You need:

Two empty bowls (or water bottles)
Food coloring
Hot water (Does not need to be boiling.)
Cold water

1. Put about the same amount of water into two bowls. One bowl should be filled with hot water from the tap. If you’re careful, you can put it in the microwave to heat it up but please don’t hurt yourself. The other bowl should have cold water in it. If you’re using water bottles, pour the hot and cold water into each bottle.

2. Let both bowls sit for a little bit (a minute or so) so that the water can come to rest.

3. Put food coloring in both bowls (or bottles) and watch carefully.

The food coloring should have spread around faster in the hot water bowl than in the cold water bowl. Can you see why? Remember that both bowls are filled with millions and millions of molecules. The food coloring is also bunches of molecules. Imagine that the molecules from the water and the molecules from the food coloring are crashing into one another like the beans on the plate. If one bowl has a higher temperature than the other, does one bowl have faster moving molecules? Yes, the higher temperature means a higher thermal energy. So the bowl with the warmer water has faster moving molecules which crash more and harder with the food coloring molecules, spreading them faster around the bowl.

If you’re using a bottle, you can do an extra step: For bottles, place a business card over the cold bottle and invert the cold bottle over the hot. Remove card.

[/am4show]

Making Clouds

Sunday September 5, 2010

Indoor Rain Clouds

Making indoor rain clouds demonstrates the idea of temperature, the measure of how hot or cold something is. Here’s how to do it:

Take two clear glasses that fit snugly together when stacked. (Cylindrical glasses with straight sides work well.)

Fill one glass half-full with ice water and the other half-full with very hot water (definitely an adult job – and take care not to shatter the glass with the hot water!). Be sure to leave enough air space for the clouds to form in the hot glass.

[am4show have=’p8;p9;p23;p50;p151;p67;p73;p82;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Place the cold glass directly on top of the hot glass and wait several minutes. If the seal holds between the glasses, a rain cloud will form just below the bottom of the cold glass, and it actually rains inside the glass! (You can use a damp towel around the rim to help make a better seal if needed.)

Materials:

glass of ice water
glass of hot water (see video)
towel
adult help

Download Student Worksheet & Exercises

Bottling Clouds

On a stormy, rainy afternoon, try bottling clouds — using the refrigerator! Here’s what you do: Place an empty, clean 2-liter soda bottle in the fridge overnight. Take it out and get an adult to light a match, letting it burn for a few seconds, then drop it into the bottle. Immediately cap the bottle and watch what happens (you should see smoke first, then clouds forming inside). Squeeze the sides of the bottle. The clouds should disappear. When you release the bottle, the clouds should reappear. Materials:

2L soda bottle
rubbing alcohol
bicycle pump
car tire valve (drill a 1/2 inch hole through a 2L soda bottle cap and pull the valve gently through with pliers)

Advanced Idea: You can substitute rubbing alcohol and a bicycle pump for the matches to make a more solid-looking cloud. Swirl a bit of rubbing alcohol around inside the bottle, just enough to coat the insides, and then pour it out. Cap your bottle with a rubber stopper fitted with a needle valve (so the valve is poking out of the bottle), and apply your pump. Increase the pressure inside the bottle (keep a firm hand on the stopper or you’ll wind up firing it at someone) with a few strokes and pull out the stopper quickly. You should see a cloud form inside.

What’s going on? Invisible water vapor is all around us, all the time, but they normally don’t stick together. When you squeezed the sides of the bottle, you increased the pressure and squeezed the molecules together. Releasing the bottle decreases the pressure, which causes the temperature to drop. When it cools inside, the water molecules stick to the smoke molecules, making a visible cloud inside your bottle.

Did you know that most drops of water actually form around a dust particle? Up in the sky, clouds come together when water vapor condenses into liquid water drops or ice crystals. The clouds form when warm air rises and the pressure is reduced (as you go up in altitude). The clouds form at the spot where the temperature drops below the dew point.

The alcohol works better than the water because it evaporates faster than water does, which means it moves from liquid to vapor more easily (and vividly) than regular old water.

Questions to ask:

How many times can you repeat this?
Does it matter what size the bottle is?
What if you don’t chill the bottle?
What if you freeze the bottle instead?

Exercises

Which combination made it rain the best? Why did this work?
Draw your experimental diagram, labeling the different components:
Add in labels for the different phases of matter. Can you identify all three states of matter in your experiment?

[/am4show]

Peanut Energy

Sunday September 5, 2010

This experiment is for advanced students. Did you know that eating a single peanut will power your brain for 30 minutes? The energy in a peanut also produces a large amount of energy when burned in a flame, which can be used to boil water and measure energy.

Peanuts are part of the bean family, and actually grows underground (not from trees like almonds or walnuts). In addition to your lunchtime sandwich, peanuts are also used in woman’s cosmetics, certain plastics, paint dyes, and also when making nitroglycerin.

What makes up a peanut? Inside you’ll find a lot of fats (most of them unsaturated) and antioxidants (as much as found in berries). And more than half of all the peanuts Americans eat are produced in Alabama. We’re going to learn how to release the energy inside a peanut and how to measure it.

[am4show have=’p9;p50;p88;p91;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

raw peanuts
chemistry stand with glass test tube and holder (watch video)
flameproof surface (large ceramic tile or cookie sheet)
paper clip
alcohol burner or candle with adult help
fire extinguisher

Download Student Worksheet & Exercises

What’s Going On? There’s chemical energy stored inside a peanut, which gets transformed into heat energy when you ignite it. This heat flows to raise the water temperature, which you can measure with a thermometer. You should find that your peanut contains 1500-2100 calories of energy! Now don’t panic… this isn’t the same as the number of calories you’re allowed to eat in a day. The average person aims to eat around 2,000 Calories (with a capital “C”). 1 Calorie = 1,000 calories. So each peanut contains 1.5-2.1 Calories of energy (the kind you eat in a day). Do you see the difference?

But wait… did all the energy from the peanut go straight to the water, or did it leak somewhere else, too? The heat actually warmed up the nearby air, too, but we weren’t able to measure that. If you were a food scientist, you’d use a nifty little device known as a bomb calorimeter to measure calorie content. It’s basically a well-insulated, well-sealed device that catches nearly all the energy and flows it to the water, so you get a much more accurate temperature reading. (Using a bomb calorimeter, you’d get 6.1-6.8 Calories of energy from one peanut!)

How do you calculate the calories from a peanut?

Let’s take an example measurement. Suppose you measured a temperature increase from 20 °C to 100 °C for 10 grams of water, and boiled off 2 grams. We need to break this problem down into two parts – the first part deals with the temperature increase, and the second deals with the water escaping as vapor.

The first basic heat equation is this:

Q = m c T

Q is the heat flow (in calories)
m is the mass of the water (in grams)
c is the specific heat of water (which is 1 degree per calorie per gram)
and T is the temperature change (in degrees)

So our equation becomes: Q = 10 * 1 * 80 = 800 calories.

If you measured that we boiled off 2 grams of water, your equation would look like this for heat energy:

Q = L m

L is the latent heat of vaporization of water (L= 540 calories per gram)
m is the mass of the water (in grams)

So our equation becomes: Q = 540 * 2 = 1080 calories.

The total energy needed is the sum of these two:

Q = 800 calories + 1080 calories = 1880 calories.

[/am4show]

Boiling Room Temperature Water

Sunday September 5, 2010

The triple point is where a molecule can be in all three states of matter at the exact same time, all in equilibrium. Imagine having a glass of liquid water happily together with both ice cubes and steam bubbles inside, forever! The ice would never melt, the liquid water would remain the same temperature, and the steam would bubble up. In order to do this, you have to get the pressure and temperature just right, and it’s different for every molecule.

The triple point of mercury happens at -38^oF and 0.000000029 psi. For carbon dioxide, it’s 75psi and -70^oF. So this isn’t something you can do with a modified bike pump and a refrigerator.

However, the triple point of water is 32^oF and 0.089psi. The only place we’ve found this happening naturally (without any lab equipment) is on the surface of Mars.

Because of these numbers, we can get water to boil here on Earth while it stays at room temperature by changing the pressure using everyday materials. (If you have a vacuum pump, you can have the water boil at the freezing point of 32^oF.)

Here’s what you need to do:

[am4show have=’p8;p9;p23;p50;p88;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

plastic syringe (no needle)
room temperature water

Bonus Idea: Do this experiment first with water, then with carbonated water.

Why does that work? How did you get the pressure to decrease? Easy – when you pulled on the plunger and increased the volume inside the syringe. Since your finger covered the hole, no additional air was allowed in when you did this (which is why it was probably a little tough to do), so the number of molecules inside the syringe stayed the same, but the space they had to wiggle around got a lot bigger, meaning that the pressure decreased.

The air inside the syringe isn’t just plain old air… it has water vapor inside, too. And that’s not all – the water from your sink isn’t just plain old water, it has air bubbles mixed in with it. When you brought down the pressure (by pulling the plunger), you are forcing the air bubbles to come out of the water, which makes it boil. When you shove the plunger back in and increase the pressure, you’ll find that the air bubbles mix back into the water and disappears.

Did you try the soda water yet? Soda has carbon dioxide already mixed in for you, which is under pressure. You can release this pressure by opening the bottle (you’ll hear a PSSST!), which is the carbon dioxide bubbles coming out of the soda. Go ahead and try that now before reading further…

When you place the soda water into the syringe and decrease the pressure, the carbon dioxide comes out quickly Try tapping the syringe to make all the tiny bubbles combine into one larger bubble. When you increase the pressure (push the plunger back in), some of the bubbles will redissolve back into the soda.

If you’ve ever had a glass of hot water suddenly erupt in an explosion of bubbles, you’ve experienced superheated water (water that’s above it’s normal boiling point) that hasn’t been able to form bubbles yet. By adding a tea bag or simply just jiggling it around is usually enough to cause the bubbles to start, which often splatters HOT HOT water everywhere. (This isn’t something you want to try without adult help.)

[/am4show]

Stairstep Candles

Sunday September 5, 2010

Fire is a chemical reaction (combustion) involving hot gases and plasma. The three things you need for a flame are oxygen, fuel, and a spark. When the fuel (gaseous wax) and oxygen (from the air) combine in a flame, one of the gases produced is carbon dioxide.

Most people think of carbon dioxide as dry ice, and are fascinated to watch the solid chunk sublimate from solid straight to gas, skipping the liquid state altogether. You’ve seen the curls of dry ice vapor curl down and cover the floor in a thick, wispy fog. Is carbon dioxide always more dense than air, or can we get it to float?

[am4show have=’p8;p9;p23;p50;p88;p91;’ guest_error=’Guest error message’ user_error=’User error message’ ]
The answer is… yes! Here’s an experiment that will walk you through how to create a hot, invisible cloud of carbon dioxide and detect where that cloud is.

Materials:

three candles
adult help
blocks or stones
LARGE jar that fits over all three candles (watch video)

Download Student Worksheet & Exercises

Carbon dioxide changes volume when you heat or cool it. When you heat the CO₂, the volume expands, lowering the density to less than that of air. When the CO₂ cools, the cloud contracts (gets smaller), and the density increases as it falls to the floor.

Remember density is mass per unit volume. So it’s an inverse relationship – when volume goes up, density goes down. In this experiment, when the temperature goes up, the volume goes up, and the density goes down.
[/am4show]

Soaking Up Rays

Sunday September 5, 2010

Heat is transferred by radiation through electromagnetic waves. Remember, when we talked about waves and energy? Well, heat can be transferred by electromagnetic waves. Energy is vibrating particles that can move by waves over distances right? Well, if those vibrating particles hit something and cause those particles to vibrate (causing them to move faster/increasing their temperature) then heat is being transferred by waves. The type of electromagnetic waves that transfer heat are infra-red waves. The Sun transfers heat to the Earth through radiation.

If you hold your hand near (not touching) an incandescent light bulb until you can feel heat on your hand, you’ll be able to understand how light can travel like a wave. This type of heat transfer is called radiation.

Now don’t panic. This is not a bad kind of radiation like you get from x-rays. It’s infra-red radiation. Heat was transferred from the light bulb to your hand. The energy from the light bulb resonated the molecules in your hand. (Remember resonance?) Since the molecules in your hand are now moving faster, they have increased in temperature. Heat has been transferred! In fact, an incandescent light bulb gives off more energy in heat then it does in light. They are not very energy efficient.

Now, if it’s a hot sunny day outside, are you better off wearing a black or white shirt if you want to stay cool? This experiment will help you figure this out:

[am4show have=’p8;p9;p23;p50;p71;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

You need:

2 ice cubes, about the same size.
A white piece of paper
A black piece of paper
A sunny day

Download Student Worksheet & Exercises

1. Put the two pieces of paper on a sunny part of the sidewalk.

2. Put the ice cubes in the middle of the pieces of paper.

3. Wait.

What you should eventually see, is that the ice cube on the black sheet of paper melts faster then the ice cube on the white sheet. Dark colors absorb more infra-red radiation then light colors. Heat is transferred by radiation easier to something dark colored then it is to something light colored and so the black paper increased in temperature more then the white paper.

So, to answer the shirt question, a white shirt reflects more infra-red radiation so you’ll stay cooler. White walls, white cars, white seats, white shorts, white houses, etc. all act like mirrors for infra-red (IR) radiation. Which is why you can aim your TV remote at a white wall and still turn on the TV. Simply pretend the wall is a mirror (so you can get the angle right) and bounce the beam off the wall before it gets to your TV. It looks like magic!

Click over to this experiment to learn how to make Liquid Crystals.

[/am4show]

Liquid Crystals

Sunday September 5, 2010

If you’ve completed the Soaking Up Rays experiment, you might still be a bit baffled as to why there’s a difference between black and white. Here’s a great way to actually “see” radiation by using liquid crystal thermal sheets.

You’ll need to find a liquid crystal sheet that has a temperature range near body temperature (so it changes color when you warm it with your hands.)

[am4show have=’p8;p9;p23;p50;p71;p84;p88;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]
The liquid crystal sheet is temperature-sensitive. When the sheet received heat from the bulb, the temperature goes up and changes color. The plastic sheets remain black except for the temperature range in which they display a series of colors that reflect the actual temperature of the crystal.

Materials:

hands
Thermal paper (AKA: Liquid Crystal Sheet)
Incandescent light bulb (or sunny day)
Silver highlighter or aluminum foil

1. Color half of the back side of the thermal paper (the side that doesn’t change color) with the highlighter (or cover half of it with foil).

2. Hold it in a position where you can easily see the color-changing side while keeping the light source on the back side.

3. Which side changes color? Is there a difference between the silver and black halves?

You’ll notice that the black half almost immediately changes color, while the silver side stays black. The silver coating reflects the heat, keeping it cool. The black side absorbs the heat and raises its temperature.

Why do liquid crystals change color with temperature? Your liquid crystal sheet is not just one sheet, but a stack of several sheets that are slightly offset from each other. The distance between each layer changes as the sheet warms up – the hotter the temperature, the closer the stacks twist together. The color they emit depends on the distance between the sheets.

The molecules that make up the sheets are long and thin, like hot dogs. When the sheets are cooler, these molecules move around less and don’t twist up as much, which corresponds to reflecting back a redder light. When the temperature rises, the molecules move around more and twist together, and they reflect a bluer light. When the liquid crystal sheet is black, all the light is absorbed (no light gets reflected).

[/am4show]

Simple Microscope & Telescope

Wednesday September 1, 2010

Did you know you can create a compound microscope and a refractor telescope using the same materials? It’s all in how you use them to bend the light. These two experiments cover the fundamental basics of how two double-convex lenses can be used to make objects appear larger when right up close or farther away.

Things like lenses and mirrors can bend and bounce light to make interesting things, like compound microscopes and reflector telescopes. Telescopes magnify the appearance of some distant objects in the sky, including the moon and the planets. The number of stars that can be seen through telescopes is dramatically greater than can be seen by the unaided eye.

Materials

A window
Dollar bill
Penny
Two hand-held magnifying lenses
Ruler

[am4show have=’p8;p9;p17;p44;p67;p73;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Place a penny on the table.
Hold one magnifier above the penny and look through it.
Bring the second magnifying lens above the first so now you’re looking through both. Move the second lens closer and/or further from the penny until the penny comes into sharp focus. You’ve just made a compound microscope.
Who’s inside the building on an older penny?
Try finding the spider/owl on the dollar bill. (Hint: It’s in a corner next to the “1”.)
Keeping the distance between the magnifiers about the same, slowly lift up the magnifiers until you’re now looking through both to a window.
Adjust the distance until your image comes into sharp (and upside-down) focus. You’ve just made a refractor telescope, just like Galileo used 400 years ago.
Find eight different items to look at through your magnifiers. Make four of them up-close so you use the magnifiers as a microscope, and four of them far-away objects so you use the magnifiers like a telescope. Complete the data table.

What’s Going On?

What I like best about this activity is how easily we can break down the basic ideas of something that seems much more complex and intimidating, like a telescope or microscope, in a way that kids really understand.

When a beam of light hits a different substance (like a window pane or a lens), the speed at which the light travels changes. (Sound waves do this, too!) In some cases, this change turns into a change in the direction of the beam.

For example, if you stick a pencil is a glass of water and look through the side of the glass, you’ll notice that the pencil appears shifted. The speed of light is slower in the water (140,000 miles per second) than in the air (186,282 miles per second). This is called optical density, and the result is bent light beams and broken pencils.

You’ll notice that the pencil doesn’t always appear broken. Depending on where your eyeballs are, you can see an intact or broken pencil. When light enters a new substance (like going from air to water) perpendicular to the surface (looking straight on), refractions do not occur.

However, if you look at the glass at an angle, then depending on your sight angle, you’ll see a different amount of shift in the pencil. Where do you need to look to see the greatest shift in the two halves of the pencil?

Why does the pencil appear bent? Is it always bent? Does the temperature of the water affect how bent the pencil looks? What if you put two pencils in there?

Depending on if the light is going from a lighter to an optically denser material (or vice versa), it will bend different amounts. Glass is optically denser than water, which is denser than air.

Not only can you change the shape of objects by bending light (broken pencil or whole?), but you can also change the size. Magnifying lenses, telescopes, and microscopes use this idea to make objects appear different sizes.

Exercises

Can light change speeds?
Can you see ALL light with your eyes?
Give three examples of a light source.
What’s the difference between a microscope and a telescope?
Why is the telescope image upside-down?

[/am4show]

Microwhat?

Saturday July 31, 2010

Welcome to our unit on microscopes! We’re going to learn how to use our microscope to make things appear larger so we can study them more easily. Think about all the things that are too small to study just with your naked eyeballs: how many can you name?

Let’s start from the inside out – before you haul out your own microscope, we’re going to have a look at what it can do. I’ve already prepared a set of slides for you below. Take out a sheet of paper and jot down your guesses – here’s how you do it:

[am4show have=’p8;p9;p26;p53;p74;p86;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]

What is it?

Take a peek and see if you can figure out what each one is. Record your guess on a piece of paper. Don’t spend more than 90 seconds on each one. If you’re working with others, have everyone write down their answers individually, and then work together and discuss each one. Come up with a final group conclusion what’s on each slide before peeking at the answers.

Need answers? Hover your mouse over each slide to reveal the title.

Care and Cleaning

1. Pick up the microscope with two hands. Always grab the arm with one hand and the legs (base) with the other.

2. Don’t touch the lenses with your fingers. The oil on your fingers will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of toilet paper and paper towels – they will scratch your lenses.

3. When you’re done with your scope for the day, reset it so that it’s on the lowest power of magnification and lower the stage to the lowest position. Cover it with your dust cover or place it in its case.

How to Use a Microscope: Optics, Observing, and Drawing Techniques

Saturday July 31, 2010

How do the lenses work to make objects larger? We’re going to take a closer look at optics, magnification, lenses, and how to draw what you see with this lesson. Here’s a video to get you started:

Here’s what you do:

[am4show have=’p8;p9;p26;p53;p74;p86;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]
1. Take a look at the eyepiece of your microscope. Do you see a number followed by an X? That tells you the magnification of your microscope. If it’s a 10X, then it will make objects appear ten times larger than usual.

2. Peek at the objective lenses. They’re on the nose of the microscope, and there’s usually 3 or 4 of them. Do you see the little numbers printed on the side of the lenses, also followed by an X? Find the one that says 4. if you look through just that lens by itself, objects will appear 4 times as large. However, it’s in a microscope, so you’re actually looking through two lenses when you use the microscope. What that means is that you need to multiply this number by the eyepiece magnification (in our example, it’s 4 * 10 = 40) to get the total power of magnification when you use the microscope on this power setting. It’s 40X when you use the 10X eyepiece and 4X objective. So objects are going to appear 40 times larger than in real life.

3. Practice these with your microscope – here are the settings on my microscope – help me fill out the table to figure out how to set the lenses for the different magnification powers:

Eyepiece	Objective	Total Magnification
10X	4X
10X		100X
	40X	400X
10X		1000X

Questions to Ask:

1. What does this table above look like for your microscope?

2. Your microscope may have come with an additional eyepiece. If so, add it to your table and figure out the range of magnification you have.

3. What is your highest power of magnification? Set it now.

4. List three possible combination of eyepiece and objective lenses if the power of magnification is 100X.

Learning to Look

Do how do you use this microscope thing, anyway? Here’s how you prepare, look, and adjust so you can get a great view of the micro world:

Download Student Worksheet & Exercises

1. Carefully cut a single letter (like an “a” or “e”) from a printed piece of paper (newspaper works well).

2. Use your tweezers to place the small letter on a slide and place a coverslip over it (be careful with these – they are thin pieces of glass that break easily!) If your letter slides around, add a drop of water and it should stick to the slide.

3. Lower the stage to the lowest setting using the coarse adjustment knob (look at the stage when you do this, not through the eyepiece).

4. Place your slide in the stage clips.

5. Turn the diaphragm to the largest hole setting (open the iris all the way).

6. Move the nose so that the lowest power objective lens is the one you’re using.

7. Bring the stage up halfway and peek through the eyepiece.

8. If you’re using a mirror, rotate the mirror as you look through the eyepiece until you find the brightest spot. You’ll probably only see a fuzzy patch, but you should be able to tell bright from dim at this point.

9. Use the coarse adjust to move the stage slowly up to bring it into rough focus. If you’ve lowered the stage all the way in step 7, you’ll see it pop into focus easily. (Be careful you don’t ram the stage into the lens!)

10. Use the fine adjust to bring it into sharp focus. What do you see?

Drawing What You See

Learning to sketch what you see is important so that the view is useful to more than just you. Here’s the easy way to do it: get a water glass and trace around the rim on a sheet of paper with your pencil. This gives you a nice, large circle that represents your scope’s field of view (what you see when you look into the microscope). Now you’re ready for the next step:

1. Draw a picture of that the letter looks like under the lowest power setting in your first circle and label it ‘right side up’. Then give the slide a half turn and draw another picture in a new circle. Label this one ‘upside-down’.

2. If you’re using a mechanical stage (which we highly recommend), twist one of the knobs so that the slide physically moves to the right as you look from the side (not through the eyepiece) of the microscope. If you’re using stage clips, just nudge the slide to the right with your finger. Now peek through the eyepiece as you move the slide to the right – which way does your letter move?

3. Now do the same for the other direction – make the slide move toward you. Which way does the letter appear to move when you look through the eyepiece?

4. What effect do the two lenses have on the letter image as you move it around? (Need a hint? Look back at the Microscope Optics Lesson from Unit 9)

Look back at your two drawings above. Let’s make them so they are totally useful, the way scientists label their own sketches. We’re going to add a border, title, power of magnification, and more to get you in the habit of labeling correctly. Here’s how you do it:

Border You need to frame the picture so the person looking at it knows where the image starts and ends. Use a water glass to help make a perfect circle every time. When I sketch at the scope, I’ll fill an entire page with circles before I start so I can quickly move from image to image as I switch slides.

Title What IS it? Paramecia, goat boogers, or just a dirty slide? Let everyone (including you!) know what it is by writing exactly what it is. You can use bold lettering or underline to keep it separate from any notes you take nearby.

Magnification Power This is particularly useful for later, if you need to come back and reference the image. You’ll be quickly and easily able to duplicate your own experiment again and again, because you know how it was done.

Proportions This is where you need to draw only what you see. Don’t make the image larger or smaller – just draw exactly what you see. If it’s got three legs and is squished in the upper right corner, then draw that. Most people draw their image smaller than it really is when viewed through the eyepiece. If it helps, mentally divide the circle into four quarters and look at each quarter-circle and make it as close to what you see as you can.

Exercises

Why do we use microscopes?
What’s the highest power of magnification on your microscope? Lowest?
Where are the two places you should NEVER touch on your microscope?
Fill in the blanks with the appropriate word to describe care and cleaning of your microscope:fingers lowest handsarm toilet paper legs dust cover
1. Pick up the microscope with two ________. Always grab the _________with one hand and the _______(base) with the other.
3. Don’t touch the lenses with your _________. The oil will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of ____________ and paper towels – they will scratch your lenses.
5. When you’re done with your scope for the day, reset it so that it’s on the _________ power of magnification and lower the stage to the lowest position. Cover it with your __________ or place it in its case.
What things must be present on your drawing so others know what they’re looking at?
What’s the proper way to use the coarse adjustment knob so you don’t crack the objective lens?
List three possible combination of eyepiece and objective lenses if the power of magnification is 100X.
Briefly describe how to dry mount a slide.
How could you view a copper penny with your microscope?

[/am4show]

Preparing a Dry Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!

This is simplest form of slide preparation! All you need to do is place it on the slide, use a coverslip (and you don’t even have to do that if it’s too bumpy), and take a look through the eyepiece. No water, stains, or glue required.

You know that this is the mount type you need when your specimen doesn’t require water to live. Good examples of things you can try are cloth fibers (the image here is of cotton thread at 40X magnification), wool, human hair, salt, and sugar. It’s especially fun to mix up salt and sugar first, and then look at it under the scope to see if you can tell the difference.

[am4show have=’p8;p9;p26;p53;p74;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Here’s what you do:

1. Pull a hair from your head and lay it on a slide. If it’s super-curly, use a bit of tape at either end, stretching it along the length of the slide. Keep the tape near the ends so it doesn’t come into your field of view when you look through the microscope.

2. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

3. Place the slide on the stage in your clips.

4. Focus the hair by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

5. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

6. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.

Don’t forget to check the windowsills for interesting bits. Use baby food jars or film canisters to collect your specimens in and keep them safe until you need them.

TIP: If you want to keep your specimen on the slide for a couple of months, use a drop of super glue and lay a coverslip down on top, pressing gently using a toothpick (not your fingers) to get the air bubbles out. Let dry.

[/am4show]

Preparing a Wet Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!

Anytime you have a specimen that needs water to live, you’ll need to prepare a wet mount slide. This is especially useful for looking at pond water (or scum), plants, protists (single-cell animals), mold, etc. When you keep your specimen alive in their environment, you not only get to observe it, but also how it eats, lives, breathes, and interacts in its environment.

[am4show have=’p8;p9;p26;p53;p74;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]

The first thing you need to do is collect your pond water. Make sure it has lots of good stuff in it! You’ll need a 20mL sample. Once you have it, place it on a table along with your microscope, slides, cover slips, tweezers, and dropper. If you’re using Protoslo (if critters are too fast, this slow them down for easier viewing), get that out, too. Open up your science notebook, draw a bunch of circles for drawing borders, and then watch this video:

Download Student Worksheet & Exercises

1. Place a slide on the table.

2. Fill the eyedropper with pond water and place a drop on the slide.

3. Place the edge of the cover slip on the pond water drop, holding the other edge up at an angle. Slowly lower the end down so that the drop spreads out. You want a very thin film to lay on the slide without any air bubbles or excess water squirting out. If you go have bubbles, gently press down on the cover slip to squish them out or start over.

4. Take time practicing this – you want the water only under the coverslip. Dab away excess water that’s not under the slide with a paper towel.

5. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

6. Place the slide on the stage in your clips.

7. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

8. Adjust the light level to get the greatest contrast so you can see better.

9. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.

8. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

9. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.

NOTE: If the critters you’re looking at move too fast, add a drop of Protoslo to the edge of your slide to slow them down (by numbing them). The Protoslo will work its way under the cover slip.

Exercises

Why do we use a wet mount slide?
Give one example of a specimen that would use a wet mount slide?
How do you prepare a wet mount slide?
Why do we stain specimens?
Give one example of a specimen that would use a stain.
What type of stain can we use (give at least one example).

[/am4show]

Slide Preparation: Staining

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount activities before you start here!

If your critter is hard to see, you can use a dye to bring out the cell structure and make it easier to view. There are lots of different types of stains, depending on what you’re looking at.

The procedure is simple, although kids will probably stain not only their specimens, but the table and their fingers, too. Protect your surfaces with a plastic tablecloth and use gloves if you want to.

We’re going to use an iodine stain, which is used in chemistry as an indicator (it turns dark blue) for starch. This makes iodine a good choice when looking at plants. You can also use Lugol’s Stain, which also reacts with starch and will turn your specimen black to make the cell nuclei visible. Methylene blue is a good choice for looking at animal cells, blood, and tissues.

In addition to your specimen, you’ll need to get out your slides, microscope, cover slips, eye dropper, tweezers, iodine (you can use regular, non-clear iodine from the drug store), and a scrap of onion. If you can find an elodea leaf, add it to your pile (check with your local garden store). Here’s what you do:

[am4show have=’p8;p9;p26;p53;p74;p86;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

1. Fill a container with water and add a small piece of elodea leaf and onion. You’ll want the onion to be a thin slice, no more than a quarter of an inch thick.

2. Practice making a wet mount first. Put a fresh slide on the table. Using tweezers, pull off a thin layer of onion (use a layer from the middle, not the top) and place it on your slide. Gently stretch out the wrinkles (use a toothpick or tweezers) and add a small drop of water and cover with a cover slip. Take a peek at what your specimen looks like on low power – do you notice it’s hard to see much? Draw what you see in your notebook.

3. Now increase the power and look again. Draw a new sketch in your notebook.

4. Now we’re going to highlight the cell structure using iodine. Lugol’s is also iodine, but the regular brown stuff from the drug store works, too. Grab a bottle of the one you’re going to use.

5. To stain the specimen, we’re going to add the stain to one side of the cover slip and wick away the water from the other side. Use a folded piece of tissue paper and touch it lightly to one side of the cover slip as you add a single drop of stain to the other side. When the stain has flowed through the entire specimen, take a peek and draw what you see in a a fresh circle.

6. Do the same thing with the elodea leaf. And anything else plant-based from your backyard. Or refrigerator. Draw what you see and don’t forget to label it with a title and power of magnification!

Exercises

Why do we use a wet mount slide?
Give one example of a specimen that would use a wet mount slide?
How do you prepare a wet mount slide?
Why do we stain specimens?
Give one example of a specimen that would use a stain.
What type of stain can we use (give at least one example).

[/am4show]

Slide Preparation: Heat Fixes

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount and Staining activities before you start here!

If you tried looking at animal cells already, you know that they wiggle and squirm all over the place. And if you tried looking when using the staining technique, you know it only makes things worse.

The heat fix technique is the one you want to use to nail your specimen to the slide and also stain it to bring out the cell structure and nuclei. This is the way scientists can look at things like bacteria.

You’re going to need your microscope, slides, cover slips, eyedropper, toothpicks or tweezers, candle and matches (with adult help), stain (you can use regular iodine or Lugol’s Stain), sugar, yeast, and a container to mix your specimen in. Here’s what you do:

[am4show have=’p8;p9;p26;p53;p74;p86;p87;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

1. Fill your container with warm water. Add about a tablespoon of yeast (one packet is enough) along with a teaspoon of sugar. The warm water activates the yeast and the sugar feeds it. You should see a foam top form in about 10 minutes.

2. Using your eyedropper, grab a bit of your sample (you want the liquid, not the foam) and place a drop on a fresh slide. Spread the drop out with a toothpick. You want to smear it into a thin layer.

3. Light the candle (with adult help). Heat the slide in the flame by gently waving it back and forth. Don’t stop it in the flame, or you’ll get black soot on the underside of the slide and possibly crack it because the glass heats up and expands too fast. You also don’t want to cook the yeast, as it will destroy what you want to look at. Just wave it around to evaporate the water.

4. Add a drop of iodine (or stain) to the slide. Wait 15 seconds.

5. Rinse it under water. (You can optionally stain it again if you find it’s particularly difficult to see your specimen, but make sure to look at it first before repeat staining.)

6. Place a drop of water (use a clean eyedropper) on the specimen and add the cover slip.

7. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

8. Place the slide on the stage in your clips.

9. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

10. Adjust the light level to get the greatest contrast so you can see better.

11. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.

12. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

NOTE: What other things can you look at? You can scrape the inside of your cheek with a toothpick and smear it on a fresh slide, take a mold sample from last week’s leftovers in the fridge, or…? Have fun!

Exercises

Why do we use heat fixes?
Briefly describe how to do a heat fix.
What is a specimen that needs a heat fix?

[/am4show]

PVA Slime

Wednesday June 30, 2010

Instead of using glue as a polymer (as in the slime recipes above), we're going to use PVA (polyvinyl alcohol). Most liquids are unconnected molecules bouncing around. Monomers (single molecules) flow very easily and don't clump together. When you link up monomers into longer segments, you form polymers (long chains of molecules).

Polymers don't flow very easily at all - they tend to get tangled up until you add the cross-linking agent, which buddies up the different segments of the molecule chains together into a climbing-rope design.

[am4show have='p8;p9;p79;p80;p101;' guest_error='Guest error message' user_error='User error message' ]
Materials:

PVA (polyvinyl alcohol)
Borax (sodium tetraborate)
Disposable cups
Popsicle sticks

Here's what you do:

Download Student Worksheet & Exercises

By adding borax to the mix, you cross-link the long chains of molecules together into a fishnet, and the result is a gel we call slime. PVA is used make sponges, hoses, printing inks, and plastic bags.

You can add food coloring (or a bit of liquid Ivory dish soap to get a marbled appearance). You can also add a dollop of titanium dioxide sunscreen to your slime before cross-linking it to get a metallic sheen.

[/am4show]

Bouncy Putty Slime

Wednesday June 30, 2010

The glue is a polymer, which is a long chain of molecules all hooked together like tangled noodles. When you mix the two solutions together, the water molecules start linking up the noodles together all along the length of each noodle to get more like a fishnet. Scientists call this a polymetric compound of sodium tetraborate and lactated glue. We call it bouncy putty.

Here’s what you do:

[am4show have=’p8;p9;p68;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Combine ½ cup water with one teaspoon of Borax in a cup and stir with a popsicle stick.
In another cup, mix equal parts white glue and water.
Add in a glob of glue mixture to the borax.
Stir for one second with a popsicle stick, then quickly pull the putty out of cup and play with it until it dries enough to bounce on table (3-5 minutes).
Pick up an imprint from a textured surface or print from a newspaper, bounce and watch it stick, snap it apart quickly and ooze apart slowly.

Download Student Worksheet & Exercises
[/am4show]

Football Ice Cream

Wednesday June 30, 2010

Is it hot where you live in the summer? What if I gave you a recipe for making ice cream that doesn’t require an expensive ice cream maker, hours of churning, and can be made to any flavor you can dream up? (Even dairy-free if needed?)

If you’ve got a backyard full of busy kids that seem to constantly be in motion, then this is the project for you. The best part is, you don’t have to do any of the churning work… the kids will handle it all for you!

This experiment is simple to set up (it only requires a trip to the grocery store), quick to implement, and all you need to do guard the back door armed with a hose to douse the kids before they tramp back into the house afterward.

One of the secrets to making great ice cream quickly is [am4show have=’p8;p9;p23;p50;p80;p88;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ] to be sure that the milk and cream is COLD. I will make this particular recipe, it’s usually with hundreds of kids, and our staff will stuff the milk products in the freezer for an hour or two or under hundreds of pounds of ice to make sure it’s super-cold.

If you’re going for the dairy-free kind, simply skip the milk and cream and add a bit of extra time to the chill time of your substitute ‘milk’. We’ve had the best luck with almond and soy milk. Are you ready?

Here’s what you need:

Materials:

1 quart whole milk (do not substitute, unless your child has a milk allergy, then use soy or almond milk)
1 pint heavy cream (do not substitute, unless your child has a milk allergy, then skip)
1 cup sugar (or other sweetener)
1 tsp vanilla (use non-alcohol kind)
rock salt (use table salt if you can’t find it)
lots of ice
freezer-grade zipper-style bags (you’ll need quart and gallon sizes)

Download Student Worksheet & Exercises

How does that work? Ice cream is basically “fluffy milk”. You need to whip in a lot of air into the milk fat to get the fluffy pockets that make this stuff worthwhile. The more the kids shake the bag, the faster it will turn into ice cream.

Why do we put salt on the ice?

If you live in an area where they put salt on the roads, you already know that people do this to melt the ice. But how does salt melt ice? Think about the chemistry of what’s going on. Water normally freezes at zero degrees Celsius. But salt water presses lower than zero, so the freezing point of salt water is lower than fresh water. By sprinkling salt on the roads, you’re lowering the point at which water freezes at. When you add a solute (salt) to the solvent (water) to alter the freezing point of the solution, it’s known as the “freezing point depression”.

Tips: Don’t use nonfat milk – it won’t work with this style of ice-cream making. if you’re adding fruit or chocolate bits, make sure you get those cold in advance too, or they will slow down your process as they heat your milk solution. (We usually add those bits last after the ice cream is done.)

IMPORTANT: Do NOT substitute dry ice for the water ice – the carbon dioxide gases build quickly and explode the bag, and now you have flying bits of dry ice that will burn skin upon contact. That’s not the biggest issue, though… the real problem is that now animals (like your dog) and small children pop a random piece of dry ice into their mouths, which will earn your family a visit to the ER. So stick with the regular ice from your fridge.

[/am4show]

Colored Campfires and Rainbows

Wednesday June 30, 2010

Always have a FIRE EXTINGUISHER and ADULT HELP handy when performing fire experiments. NO EXCEPTIONS.

This video will show you how to transform the color of your flames. For a campfire, simply sprinkle the solids into your flames (make sure they are ground into a fine powder first) and you’ll see a color change. DO NOT do this experiment inside your house – the fumes given off by the chemicals are not something you want in your home!

One of the tricks to fire safety is to limit your fuel. The three elements you need for a flame are: oxygen, spark, and fuel. To extinguish your flames, you’ll have to either wait for the fuel to run out or smother the flames to cut off the oxygen. When you limit your fuel, you add an extra level of safety to your activities and a higher rate of success to your eyebrows.

Here’s what we’re going to do: first, make your spectrometer: you can make the simple spectrometer or the more-advanced calibrated spectrometer. Next, get your chemicals together and build your campfire. Finally, use your spectrometer to view your flames.

[am4show have=’p8;p9;p25;p52;p91;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

This experiment is at your own risk! You MUST get an experienced adult to help you with this activity.

Boric Acid or placing a copper pipe directly in the fire will give you GREEN flames
Borax (sodium tetraborate) gives a YELLOW-GREEN flame
Epsom salts (magnesium sulfate) will give you WHITE-PURPLE flames
Table salt (sodium chloride) will give you YELLOW flames
Washing soda (sodium carbonate) will give you YELLOW-GREEN flames
Calcium Chloride (Ice Melt, Dri-Ez) will give an ORANGE flame (make sure it says ‘Calcium Chloride’ – there are a lot of other types of molecules used to melt ice!)
Potassium Chloride (Nu Salt) will give you RAINBOW flames
RED flames are made with strontium, which isn’t something you want kids to be playing with.

How to Tell Which Elements are Burning

Once you’ve got the hang of how to make colored flames, your next step is to create a spectroscope. When you aim your nifty little device at the flames, you’ll be able to split the light into its spectra and see which elements are burning. For example, if you were to view hydrogen burning with your spectroscope, you’d see the bottom appear in your spectrometer:

Notice how one fits into the other, like a puzzle. When you put the two together, you’ve got the entire spectrum.

What’s the difference between the two? The upper picture (absorption spectrum of hydrogen) is what astronomers see when they use their spectrometers on distant stars when looking through the earth’s atmosphere (a cloud of gas particles). The lower picture (emission spectrum of hydrogen) is what you’d see if you were looking directly at the source itself.

Note – Do NOT use your spectrometer to look at the sun! When astronomers look at stars, they have computers look for them – they aren’t putting their eye on the end of a tube.

What about other elements?

Each element has it’s own special ‘signature’, unique as a fingerprint, it leaves behind when it burns. This is how we can tell what’s on fire in a campfire. For example, here’s what you’d see for the following elements:

Just get the feel for how the signature changes depending on what you’re looking at. For example, a green campfire is going to look a lot different from a regular campfire, as you’re burning several elements in addition to just carbon. When you look at your campfire with your spectroscope, you’re going to see all the signatures at the same time. Imagine superimposing all four sets of spectral lines above (carbon, neon, magnesium, and nitrogen) into one single spectrum… it’s going to look like a mess! It takes a lot of hard work to untangle it and figure out which lines belong to which element. Thankfully these days, computers are more than happy to chug away and figure most of it out for us.

Here’s the giant rainbow of absorption lines astronomers see when they point their instruments at the sun:

Do you see all the black lines? Those are called emission lines, and since astronomers have to look through a lot of atmosphere to view the sun, there’s a lot of the spectrum missing (shown by the black lines), especially corresponding to water vapor. The water absorbs certain wavelengths of light, which corresponds to the black lines.

[/am4show]

Sewer Slime

Wednesday June 30, 2010

Guar gum comes from the guar plant (also called the guaran plan), and people have found a lot of different and interesting uses for it. It’s one of the primary substitutes for fat in low-fat and fat-free foods. Cooks like to use guar gum in foods as it has 8 times the thickening power of cornstarch, so much less is needed for the recipe. Ice cream makers use it to keep ice crystals from forming inside the carton. Doctors use it as a laxative for their patients.

When we teach kids how to make slime using guar gum, they call it “fake fat” slime, mostly because it’s used in fat-free baking. You can find guar gum in health food stores or order it online. We’re going to whip up a batch of slime using this “fake fat”. Ready?

Here’s what you do:
[am4show have=’p8;p9;p68;p79;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Fill a cup with 7 tablespoons of cold water.
Stir in 1/4 teaspoon of guar gum, stir with a popsicle stick 10 times and stop, leaving the stick in.
Cautiously dip a pinkie into the cup, then rub it in their fingers. Does it smell?
Leave it for 2 minutes to thicken.
In a fresh cup, mix 1 teaspoon borax (sodium tetraborate) in one tablespoon water.
Add ½ teaspoon of the Borax Solution to the Guar solution. Stir and it will form a gel that looks like real boogers!

[/am4show]

Volcanoes

Wednesday June 30, 2010

If you’ve ever wanted to make your own version of a volcano that burps and spit all over the place, then this is the experiment for you. We used to teach kids how to make genuine Fire & Flame volcanoes, but parents weren’t too happy about the shower of sparks that hit the ceiling and fireballs that shot out of the thing… so we’ve toned it down a bit to focus more on the lava flow.

[am4show have=’p8;p9;p73;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

FIRST STEP: Make the volcano.

The first thing to do is mix up your own volcano dough. You can choose from the following two mixtures. The Standard Volcano Dough is akin to play dough; the Earthy Volcano Dough looks more like the real thing. Either way, you’ll need a few days on the shelf or a half-hour in a low-temperature oven to bake it dry. Alternatively, you can use a slab of clay for the dough.

Standard Volcano Dough Mix together 6 cups flour, 2 cups salt, ½ cup vegetable oil, and 2 cups warm water. The resulting mixture should be firm but smooth. Stand a water or soda bottle in a roasting pan and mold the dough around it into a volcano shape.
Earthy Volcano Dough Mix 2½ cups flour, 2½ cups dirt, 1 cup sand, and 1½ cups salt. Add water by the cup until the mixture sticks together. Build the volcano around an empty water bottle on a disposable turkey-style roasting pan. It will dry in two days if you have the time, but why wait? You can erupt when wet if the mixture is stiff enough! (And if it’s not, add more flour until it is.)

SECOND STEP: Create the reaction.

Soda Volcanoes Fill the bottle most of the way with warm water and a bit of red food coloring. Add a splash of liquid soap and ¼ cup baking soda. Stir gently. When ready, add vinegar in a steady stream and watch that lava flow.

Air Pressure Sulfur Volcanoes Wrap the volcano dough around an 18” piece of clear, flexible tubing. Shape the dough into a volcano and place in a disposable roasting pan. Push and pull the tube from the bottom until the other end of the tube is just below the volcano tip. If you clog the ends of the tubing with clay, just trim away the clog with scissors. Using your fingers, shape the inside top of the volcano to resemble a small paper cup. Your solution needs a chamber to mix and grow in before overflowing down the mountain. The tube goes at the bottom of the clay-cup space. Be sure the volcano is SEALED to the cookie sheet at the bottom. You won’t want the solution running out of the bottom of the volcano instead of popping out the top!

- Make your chemical reactants.
  - Solution 1: Fill one bucket halfway with warm water and add 1 to 2 cups baking soda. Add 1 cup of liquid dish soap and stir very gently so you don’t make too many bubbles.

- - Solution 2: Fill a second bucket halfway with water and add 1 cup of aluminum sulfate (also called alum; find this in the gardening section of the hardware store or check the spice section of the grocery store). Add red food coloring and stir.

- - Putting it all together: Count ONE (and pour in Solution 1) … TWO (inhale air only!) …… and THREE (pour in Solution 2 as you put your lips to the tube from the bottom of the volcano and puff as hard as you can!) Lava should not only flow but burp and spit all over the place!

Download Student Worksheet & Exercises

Exercises

How is this activity similar to the volcanoes on Mars?
What gas is produced with this reaction?
Which planets have volcanoes?

[/am4show]

Water Purification

Wednesday June 30, 2010

Ever wonder how the water draining down your sink gets clean again? Think about it: The water you use to clean your dishes is the same water that runs through the toilet. There is only one water pipe to the house, and that source provides water for the dishwasher, tub, sink, washing machine, toilet, fish tank, and water filter on the front of your fridge. And there’s only one drain from your house, too! How can you be sure what’s in the water you’re using?

This experiment will help you turn not only your coffee back into clear water, but the swamp muck from the back yard as well. Let’s get started.
[am4show have=’p8;p9;p80;p84;p101;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

clean play sand
alum (check the spice section of the grocery store)
distilled water
water sample (a cup of coffee with the ground put back in works great)
activated carbon (check an aquarium store)
cheese cloth
clear disposable cups
popsicles
medicine dropper or syringe (no needle)
funnel
2 cotton balls
measuring spoon (1/4 tsp and 1/2 tsp)

Download Student Worksheet & Exercises

There are several steps you need to understand as we go along:

Aeration: Aerate water to release the trapped gas. You do this in the experiment by pouring the water from one cup to another.
Coagulation: Alum collects small dirt particles, forming larger, sticky particles called floc.
Sedimentation: The larger floc particles settle to the bottom of the cup.
Filtration: The smaller floc particles are trapped in the layer of sand and cotton.
Disinfection: A small amount of disinfectant is added to kill the remaining bacteria. This is for informational purposes only — we won’t be doing it in this experiment. (Bleach and kids don’t mix!)

Preparing the Sample

Make your “swamp muck” sample by filling a small pitcher with water, coffee, and the coffee grounds. Fill up another small pitcher with clean water. In a third small pitcher, pour a small scoop of charcoal carbon and cold water.

Fill one clear plastic cup half full of swamp muck. Stir in ½ teaspoon aluminum sulfate (also known as alum) and ¼ teaspoon calcium hydroxide (also known as lime; it’s nasty stuff to breathe in so keep it away from kids). You have just made floc, the heavy stuff that settles to the bottom.

Aside: For pH balance, you can add small amounts of lime to raise the pH (level 7 is optimal), if you have pH indicators on hand (find these at the pharmacy).

Stir it up and sniff — then don’t touch for 10 minutes as you make the filter.

Making the Filter

Grab a cotton ball and fluff it out HUGE. Then stuff it into the funnel. The funnel will take two or three balls. (Don’t stuff too hard, or nothing will get through!) Strain out the carbon granules from the pitcher, and put the black carbon water back into the pitcher. Place the funnel over a clean cup and pour the black water directly over the cotton balls. Run the dripped-out water back through the funnel a few times. Those cotton balls will turn gray-black! Discard all the carbon water.

Add a layer of sand over the top of the cotton balls. It should cover the balls entirely and come right up to the top of the funnel. Fill a third empty cup half-full of clean water from the pitcher. Drip (using a dropper) clean water into the funnel. (This gets the filter saturated and ready to filter.)

Showtime!

It’s time to filter the swamp muck. Without disturbing the sample, notice where the floc is… the dark, solid layer at the bottom. You’ve already filtered out the larger particles without using a filter! Using a dropper, take a sample from the layer above the floc (closer to the top of your container) and drip it into the funnel. If you’ve set up your experiment just right, you’ll see clear water drip out of your funnel.

Continue this process until the liquid starts to turn pale – which indicates that your filter is saturated and can’t filter out any more particles.

To dissect the filter and find out where the muck got trapped, invert the funnel over four layers of paper towel. Usually the blacker the cotton, the better the filter will work. Look for coffee grounds in the sand.

“Radioactive” Sample

Activate a disposable light stick. Break open the light stick (use gloves when handling the inner liquid), and using the dropper, add the liquid to the funnel. You can also drip the neon liquid by the drop into the swamp muck sample and pass it through your filter.

You can test out other types of “swamp muck” by mixing together other liquids (water, orange juice, etc.) and solids (citrus pulp, dirt, etc.). Stay away from carrot juice, grape juice, and beets — they won’t work with this type of filter.

[/am4show]

Calibrated Spectrometer

Wednesday June 30, 2010

Ever play with a prism? When sunlight strikes the prism, it gets split into a rainbow of colors. Prisms un-mix the light into its different wavelengths (which you see as different colors). Diffraction gratings are tiny prisms stacked together.

When light passes through a diffraction grating, it splits (diffracts) the light into several beams traveling at different directions. If you’ve ever seen the ‘iridescence’ of a soap bubble, an insect shell, or on a pearl, you’ve seen nature’s diffraction gratings.

Scientist use these things to split incoming light so they can figure out what fuels a distant star is burning. When hydrogen burns, it gives off light, but not in all the colors of the rainbow, only very specific colors in red and blue. It’s like hydrogen’s own personal fingerprint, or light signature.

While this spectrometer isn't powerful enough to split starlight, it's perfect for using with the lights in your house, and even with an outdoor campfire. Next time you're out on the town after dark, bring this with you to peek different types of lights - you'll be amazed how different they really are. You can use this spectrometer with your Colored Campfire Experiment also.

SPECIAL NOTE: This instrument is NOT for looking at the sun. Do NOT look directly at the sun. But you can point the tube at a sheet of paper that has the the sun’s reflected light on it.

Here's what you do:

[am4show have='p8;p9;p25;p52;p105;p91;p101;' guest_error='Guest error message' user_error='User error message' ]

Download Student Worksheet & Exercises

You will need:

cardboard box (ours is 10" x 5" x 5", but anything close to this will work fine)
linear diffraction grating (you can order one here)
2 razor blades (with adult help)
masking tape
ruler
photocopy of a ruler (or sketch a line with 1 through 10 cm markings on it, about 4cm wide)

1. Using a small box, measure 4.5 cm from the edge of the box. Starting here, cut a hole for the double-razor slit that is 1.5 cm wide 3 cm long.

2. From the other edge (on the same side), cut a hole to hold your scale that is 11 cm wide and 4 cm tall.

3. Print out the scale and attach it to the edge of the box.

4. Very carefully line up the two razors, edge-to-edge to make a slit and secure into place with tape.

5. On the opposite side of the box, measure over 3 cm and cut a hole for the diffraction grating that is 4 cm wide and 3 cm tall.

5. Tape your diffraction grating over the hole.

Aim the razor slit at a light source such as a fluorescent light, neon sign, sunset, light bulb, computer screen, television, night light, candle, fireplace… any light source you can find. Put the diffraction grating up to your eye and look at the inner scale. Move the spectrometer around until you can get the rainbow to be on the scale inside the box.

How to Calibrate the Spectrometer with the Scale Inside your box is a scale in centimeters. Point your slit to a fluorescent bulb, and you'll see three lines appear (a blue, a green, and a yellow-orange line). The lines you see in the fluorescent bulb are due to mercury superimposed on a rainbow continuous spectrum due to the coating. Each of the lines you see is due to a particular electron transition in the visible region of Hg (mercury). The blue line (435 nm), the green line (546 nm), and the yellow orange line (579 nm). (If you look at a sodium vapor street light you'll see a yellow line (actually 2 closely spaced) at 589 nm.)

Step 1. Line the razor slits along the length of the fluorescent tube to get the most intense lines. Move the box laterally (the lines will move due to parallax shift).

Step 2. Take scale readings at the extreme of the these movements and take the average for the scale reading. For instance, if the blue line averages to the 8.8 cm value, this corresponds to the 435 nm wavelength. Do this for the other 2 lines.

Step 3. On graph paper, plot the cm ( the ruler scale values) on the vertical axis and the wavelength (run this from 400-700 nm) on the horizontal axis. Draw the best straight lines thru the 3 points (4 lines if you use the Na (sodium) street lamp). You've just calibrated the spectrometer.

Step 4. Line the razor slits up with another light source. Notice which lines appear and where they are on your scale. Find the value on your graph paper. For example, if you see a line appear at 5.5 cm, use your finger to follow along to the 5.5 cm until you hit the best-fit line, and then read the corresponding value on the wavelength axis. You now have the wavelength for the line you've just seen!

Notes on Calibration and Construction: If you swap out different diffraction gratings, you will have to re-calibrate. If you make a new spectrometer, you will have to re-calibrate to the Hg (mercury) lines for each new spectrometer. If you do remake the box, use a scale that is translucent so you can see the numbers. If you use a clear plastic ruler, it may let in too much light from the outside making it difficult to read the emission line.

What other light sources work? Use your spectrometer to look at computer screens, laptops, night lights, neon lights, candles, campfires, fluorescent lights, incandescent lights, LEDs, stoplights, street lights, and any other light sources you can find. When you walk down town at night and look at various "neon" signs. Ne (neon) is a real burner! Do this with a friend who is willing to vouch for your sanity.

Question: What happens when you aim a laser through a diffraction grating? (See picture above - can you find the two dots on either side of the main later dot?)

[/am4show]

Pinhole Solar Projector

Wednesday June 30, 2010

You might be curious about how to observe the sun safely without losing your eyeballs. There are many different ways to observe the sun without damaging your eyesight. In fact, the quickest and simplest way to do this is to build a super-easy pinhole camera that projects an image of the sun onto an index card for you to view.

CAUTION: DO NOT LOOK AT THE SUN THROUGH ANYTHING WITH LENSES!!

This simple activity requires only these materials:

tack
2 index cards (any size)
sunlight

[am4show have=’p8;p9;p17;p44;p105;p67;p96;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you do:

Download Student Worksheet & Exercises

With your tack, make a small hole in the center of one of the cards. Stack one card about 12″ above the over and go out into the sun. Adjust the spacing between the cards so a sharp image of the sun is projected onto the lower paper. The sun will be about the size of a pea.

You can experiment with the size of the hole you use to project your image. What happens if your hole is really big? Too small? What if you bend the lower card while viewing? What if you punch two holes? Or three?

Exercises

How many longitude degrees per day does the sunspot move?
Do all sunspots move at the same rate?
Did some of the sunspots change size or shape, appear or disappear?

[/am4show]

Streaming Water

Tuesday June 1, 2010

Fill the bathtub and climb in. Grab your water bottle and tack and poke several holes into the lower half the water bottle. Fill the bottle with water and cap it. Lift the bottle above the water level in the tub and untwist the cap. Water should come streaming out. Close the cap and the water streams should stop. Open the cap and when the water streams out again, can you “pinch” two streams together using your fingers?

Materials: A tack, and a plastic water bottle with cap, and bathtub

[am4show have=’p8;p9;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]

What’s happening? First, you’re getting clean. Second, you’re playing with pressure again. Watch the water level when you uncap the bottle. As the water streams out, the water level in the bottle moves downward. Notice how the space for air increases in the top of the bottle as the water line moves down. (The air comes in through the mouth of the bottle.) When you cap on the bottle, there’s no place for air to enter the bottle. The water line wants to move down, but since there’s no incoming air to equalize the pressure, the flow of water through the holes stops. Technically speaking, there’s a small decrease in pressure in the air pocket in the top of the bottle and therefore the air outside the bottle has a higher pressure that keeps the water in the bottle. Higher pressure pushes!

[/am4show]

Sneaky Bottles

Tuesday June 1, 2010

This experiment illustrates that air really does take up space! You can’t inflate the balloon inside the bottle without the holes, because it’s already full of air. When you blow into the bottle with the holes, air is allowed to leak out making room for the balloon to inflate. With the intact bottle, you run into trouble because there’s nowhere for the air already inside the bottle to go when you attempt to inflate the balloon.

You’ll need to get two balloons, one tack, and two empty water bottles.

[am4show have=’p8;p9;p82;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Poke a balloon into a water bottle and stretch the balloon’s neck covering the mouth of the bottle from the inside. Repeat with the other bottle. Using the tack, poke several small holes in the bottom of one of the water bottles. Putting your mouth to the neck of each bottle, try to inflate the balloons.

A cool twist on this activity is to drill a larger hole in the bottle (say, large enough to be covered up by your thumb) and inflate the balloon inside the bottle with hole open, then plug up the hole with your thumb. The balloon will remain inflated even though its neck is not tied! Where is the higher pressure region now?

[/am4show]

Squished Balloon

Tuesday June 1, 2010

Fire eats air, or in more scientific terms, the air gets used up by the flame and lowers the air pressure inside the jar. The surrounding air outside the jar is now at a higher pressure than the air inside the jar and it pushes the balloon into the jar. Remember: Higher pressure pushes!

Materials: a balloon, one empty glass jar, scrap of paper towel , matches with an adult

[am4show have=’p8;p9;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Blow up a balloon so that it is just a bit larger than the opening of the jar and can’t be easily shoved in. With an adult, light the small wad of paper towel on fire and drop it into the jar. Place the balloon on top. When the fire goes out, lift the balloon. The jar goes with it!

[/am4show]

Fountain Bottle

Tuesday June 1, 2010

As you blow air into the bottle, the air pressure increases inside the bottle. This higher pressure pushes on the water, which gets forced up and out the straw (and up your nose!).

Materials: small lump of clay, water, a straw, and one empty 2-liter soda bottle.

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Fill a 2-liter soda water bottle full of water and seal it with a lump of clay wrapped around a long straw so that the straw is secured to the mouth of the bottle. (The straw should be partly submerged in the water.) Blow hard into the straw. Splash!

[/am4show]

Bubble Experiments

Monday May 31, 2010

bubble_magician_tom_noddy — Magician Tom Noddy

If you’re fascinated by the simple complexity of the standard soap bubble, then this is the lab for you. You can easily transform these ideas into a block-party Bubble Festival, or just have extra fun in the nightly bathtub. Either way, your kids will not only learn about the science of water, molecules, and surface tension, they’ll also leave this lab cleaner than they started (which is highly unusually for science experiments!)

Soap also makes water stretchy. If you’ve ever tried making bubbles with your mouth just using spit, you know that you can’t get the larger, fist-sized spit bubbles to form completely and detach to float away in the air. Spit is 94% water, and water by itself has too much surface tension, too many forces holding the molecules together. When you add soap to it, they relax a bit and stretch out. Soap makes water stretch and form into a bubble.
[am4show have=’p8;p9;p80;p101;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

The absolute best time to make gigantic bubbles is on an overcast day, right after it rains. Bubbles have a thin cell wall that evaporates quickly in direct sun, especially on a low-humidity day. If you live in a dry area with low-humidity, be sure to use glycerin. The glycerin will add moisture and deter the rapid thinning of the bubble’s cell wall (which cause bubbles to tear and pop).

Best Bubble Solution Gently mix together 6 cups cold water in a shallow tub with 1 cup green Dawn (or clear Ivory) dish soap. If it’s a hot, dry day, add a few tablespoons of glycerin. (Glycerin can be found at the drugstore.) If you’re finding the solution too thin, add a second cup of dish soap. You can add all sorts of things to find the perfect soap solution: lemon juice, sugar, corn syrup, Karo syrup, maple syrup, glycerin — to name just a few. Each will add its own properties to the bubble solution. (You can have buckets of each variation along with plain dish soap and water to compare.) You can reduce the water, increase the soap, etc… but here’s a good starting point: 2 cups dish soap with 1 cup Karo syrup and 6 cups cold water.

Zillions of Tiny Bubbles can be made with strawberry baskets. Simply dip the basket into the bubble solution and twirl around. You can also use plastic six-pack soda can holders.

Trumpet Bubbles are created by using a modified water bottle. Cut off the bottom of the bottle, dip the large end in the soap solution, put the small end to your lips, and blow. You can separate the bubble from the trumpet by rolling the large end up and away from your bubble.

Bubble Castles are built with a straw and a plate. First, spread bubble solution all over a smooth surface (such as a clean cookie sheet, plate, or tabletop). Dip one end of a straw in the bubble solution and blow bubbles all over the surface. Make larger domes with smaller ones inside. Notice how the bubbles change shape and size when they connect with others.

Stretch and Squish! Get one hand-sized bubble in each hand. Slap them together (so they join, not pop!). What if you join them s l o w l y?

Light Show is always a favorite. Find a dark room. Find a BIG flashlight and stand it on end. Rub soap solution all over the bottom of an uncolored plastic lid (such as from a coffee can). Balance the lid, soapy side up, on the flashlight (or on the spring-type clothespins). Blow a hemisphere bubble on top of the lid. Blow gently along the side of the bubble. Watch the colors swirl.

Weird Shapes are the simplest way to show how soap makes water stretchy. Dip a rubber band completely in the soap solution and pull it up. Stretch the rubber band using your fingers. Twist and tweak into all sorts of shapes. Note that the bubble always finds a way of filling the shape with the minimum amount of surface area. Make a Moebius bubble by cutting a thick ribbon, giving one end a half-twist, and reattaching the ends (by sewing, stapling, or taping).

Polygon Shapes allow you to make square and tetrahedral bubbles. Create different 3-D shapes by bending pipe cleaners into cubes, tetrahedrons, or whatever you wish. Alternatively, you can use straws threaded onto string to make 3-D triangular shapes. Notice how the film always finds its minimum surface area. Can you make square bubbles?

Gigantic Bubbles Using the straws and string, thread two straws on three feet of string and tie off. Grasp one straw in each hand and dip in soap solution. Use a gentle wind as you walk to make BIG bubbles. Find air thermals (warm pockets of air) to take your bubbles up, up, UP!

Kid-in-a-Bubble Pour your best bubble solution into a child’s plastic swimming pool. Lay a Hula-hoop down, making sure there is enough bubble solution to just cover the hoop. Have your child stand in the pool (use a stool if you want to avoid wet feet), and lift the hoop! For a more permanent project, use an old car tire sliced in half lengthwise (the hard way) to hold the bubble solution. The kid stands in the hole and doesn’t get wet!

Electric Bubbles Blow some fist-sized bubbles and set them loose. Rub an inflated balloon on your head or wool sweater to charge the balloon and get the charged balloon close to a soap bubble. If you are fast and careful enough, you can steer the bubble around the room.

Hover Bubbles Since bubbles are light, you can float them on a gas that is slightly denser than the air they are filled with, such as carbon dioxide. Place a shallow glass dish inside a larger glass dish or tank (like an unoccupied aquarium). Into the smaller dish, add two cups vinegar and one cup baking soda.

After the fizzing has subsided, your larger container is now filled with carbon dioxide gas. Make sure it’s away from drafts or movement so the invisible carbon dioxide gas stays in there. Gently blow bubbles near the opening so they settle into the large tank. (Don’t blow directly into the container, or you’ll slosh out the CO₂.) Your bubbles will hover in the tank so you can have a closer look. What colors do you see? Do the colors change? Does the bubble stay in one place, rise, sink, or move around? If your bubble stays in the tank without popping, you’ll notice that it slowly becomes larger!

Mammoth Bubbles To create bubbles the size of a small car, use your lace trim. Knot the ends together to form a large loop, and dip your lace into the bubble solution. Gently pick up the loop with your hands about two feet apart, the rest dangling below. You should see a thin bubble film in the loop. Keep your hands spread apart and walk (keeping the bottom loop above the ground), and a bubble will form behind you. When it’s big enough, close the loop by bringing your hands together to seal off the bubble. You can also spin slowly in a circle to put yourself inside a “bubble-bagel” (mathematical term for this shape: toroid). If you do this in a place with warm updrafts (like next to a building), your bubbles will float up and away and quite possibly attract a small crowd… like the photo below.

The How and Why Explanation If you pour a few droplets of water onto a sweater or fabric, you’ll notice that the water will just sit there on the surface in a ball (or oval, if the drop is large enough). If you touch the ball of water with a soapy finger, the ball disappears into the fibers of the fabric! What happened?

Soap makes water “wetter” by breaking down the water’s surface tension by about two-thirds. Surface tension is the force that keeps the water droplet in a sphere shape. It’s the reason you can fill a cup of water past the brim without it spilling over. Without soap, water can’t get into the fibers of your clothes to get them clean. That’s why you need soap in the washing machine.

The soap molecule looks a lot like a snake; it’s a long chain that has two very different ends. The head of the snake loves water, and the tail loves dirt. When the soap molecule finds a dirt particle, it wraps its tail around the dirt and holds it.

The different colors of a soap bubble come from how the white light bounces off the bubble into your eye. Some of the light bounces off the top surface of the bubble and bends only a little bit, while the rest passes through the thin film and bounces off the inner surface of the bubble and refracts more.

If you made the Hover Bubbles, you’ll notice that the bubbles slowly get larger the longer they live in the tank. Remember that the bubble is surrounded by CO₂ gas as it sinks. The bubble grows because carbon dioxide seeps through the bubble film faster than the air seeps out, as CO₂ is more soluble in water than air (meaning that CO₂ mixes more easily with water than air does).

[/am4show]

Ping Pong Funnel

Monday May 31, 2010

As you blow into the funnel, the air under the ball moves faster than the other air surrounding the ball, which generates an area of lower air pressure. The pressure under the ball is therefore lower than the surrounding air which is, by comparison, at a higher pressure. This higher pressure pushes the ball back into the funnel, no matter how hard you blow or which way you hold the funnel. The harder you blow, the more stuck the ball becomes. Cool.

Materials: A funnel and a ping pong ball

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Insert a ping pong ball into a funnel. Place the stem of the funnel between your lips and tilt your head back so ball stays inside. Blow a strong, long stream of air into the funnel.

[/am4show]

Magic Water Glass Trick

Monday May 31, 2010

Where’s the pressure difference in this trick?

At the opening of the glass. The water inside the glass weighs a pound at best, and, depending on the size of the opening of the glass, the air pressure is exerting 15-30 pounds upward on the bottom of the card. Guess who wins? Tip, when you get good at this experiment, try doing it over a friend’s head!

Materials: a glass, and an index card large enough to completely cover the mouth of the glass.

[am4show have=’p8;p9;p82;p84;p93;p100;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Fill a glass one-third with water. Cover the mouth with an index card and over a sink invert the glass while holding the card in place. Remove your hand from the card. Voila! Because atmospheric air pressure is pushing on all sides of both the glass and the card, the card defies gravity and “sticks” to the bottom of the glass. Recall that higher pressure pushes and when you have a difference in pressure, things move. This same pressure difference causes storms, winds, and the index card to stay in place.

[/am4show]

Hot Air Balloon

Monday May 31, 2010

About 400 years ago, Leonardo da Vinci wanted to fly… so he studied the only flying things around at that time: birds and insects. Then he did what any normal kid would do—he drew pictures of flying machines!

Centuries later, a toy company found his drawing for an ornithopter, a machine that flew by flapping its wings (unlike an airplane, which has non-moving wings). The problem (and secret to the toy’s popularity) was that with its wing-flapping design, the ornithopter could not be steered and was unpredictable: It zoomed, dipped, rolled, and looped through the sky. Sick bags, anyone?

Hot air balloons that took people into the air first lifted off the ground in the 1780s, shortly after Leonardo da Vinci’s plans for the ornithopter took flight. While limited seating and steering were still major problems to overcome, let’s get a feeling for what our scientific forefathers experienced as we make a balloon that can soar high into the morning sky.

Materials: A lightweight plastic garbage bag, duct or masking tape, a hand-held hair dryer. And a COLD morning.

Here’s what you do:

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Shake out a garbage bag to its maximum capacity. Using duct or masking tape, reduce the opening until it is almost-closed leaving only a small hole the size of the hair dryer nozzle. Use the hair dryer to inflate the bag, heating the air inside, but make sure you don’t melt the bag! When the air is at its warmest, release your hold on the bag while at the same time you switch off the hair dryer. The bag should float upwards and stay there for a while.

Troubleshooting: This experiment works best on cold, windless mornings. If it’s windy outside, try a cool room. The greater the temperature difference between the hot air inside the garbage bag versus the cold, still air, the faster the bag rises. The only other thing to watch for is that you’ve taped the mouth of the garbage bag securely so the hot air doesn’t seep out. Be sure the opening you leave is only the diameter of your hair dryer’s nozzle.

Want to go BIGGER? Then try the 60-foot solar tube!
[/am4show]

Diaper Wind Bag

Monday May 31, 2010

Lots of science toy companies will sell you this experiment, but why not make your own? You’ll need to find a loooooong bag, which is why we recommend a diaper genie. A diaper genie is a 25′ long plastic bag, only both ends are open so it’s more like a tube. You can get three 8-foot bags out of one pack.

Kids have a tendency to shove the bag right up to their face and blow, cutting off the air flow from the surrounding air into the bag. When they figure out this experiment and perform it correctly, this is one of those oooh-ahhh experiments that will leave your kids with eyes as big as dinner plates.

Here’s what you do:

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Cut an eight-foot section of the diaper genie bag and knot one of the ends. Hold the other end open, take a deep breath, and blow. How many breaths does it take for you to fill up the entire bag with air? Try this now…

After you know how many breaths it takes, do you think you can fill the bag with only ONE breath? The answer is YES! Hold the bag about eight inches from the face and blow long and steady into the bag. As soon as you run out of air, close the end of the bag and slide your hand along the length (toward the knotted end) until you have an inflated blimp.

Troubleshooting: If the bag tears open, use packing tape to mend it.

What’s going on? When you blow air past your lips, a pocket of lower air pressure forms in front of your face. The stronger you blow, the lower the air pressure pocket. The air surrounding this lower pressure region is now at a higher pressure than the surrounding air, which causes things to shift and move. When you blow into the bag (keeping the bag a few inches from your face), you build a lower pressure area at the mouth of the bag, and the surrounding air rushes forward and into the bag.

Substitution Tip: If you can’t locate a diaper genie, you can string together plastic sheets from garbage bags, using lightweight tape to secure the seams. You’ll need to make a 8-12” diameter by eight-foot long tube and close one end. When kids get their eight-foot bag inflated in just one breath, ask them: “Did you really have that much air in your lungs?”

[/am4show]

Genie in a Bottle

Monday May 31, 2010

While this isn’t actually an air-pressure experiment but more of an activity in density, really, it’s still a great visual demonstration of why Hot Air Balloons rise on cold mornings.

Imagine a glass of hot water and a glass of cold water sitting on a table, side by side. Now imagine you have a way to count the number of water molecules in each glass. Which glass has more water molecules?

The glass of cold water has way more molecules… but why? The cold water is more dense than the hot water. Warmer stuff tends to rise because it’s less dense than colder stuff and that’s why the hot air balloon in experiment 1.10 floated up to the sky.

Clouds form as warm air carrying moisture rises within cooler air. As the warm, wet air rises, it cools and begins to condense, releasing energy that keeps the air warmer than its surroundings. Therefore, it continues to rise. Sometimes, in places like Florida, this process continues long enough for thunderclouds to form. Let’s do an experiment to better visualize this idea.

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials: Two identical tall glasses, hot water, cold water, red and blue food dye, and an index card larger enough to cover the opening of the glasses

Fill two identical water glasses to the brim: one with hot water, the other with cold water. Put a few drops of blue dye in the cold water, a few drops of red dye in the hot water. Place the index card over the mouth of the cold water and invert the glass over the glass of hot water. Line up the openings of both glasses, and slowly remove the card.

Troubleshooting: Always invert the cold glass over the hot glass using an index card to hold the cold water in until you’ve aligned both glasses. You can also substitute soda bottles for water glasses and slide a washer between the two bottles to decrease the flow rate between the bottles so the effect lasts longer.

[/am4show]

Soda Can Trick

Monday May 31, 2010

When air moves, the air pressure decreases. This creates a lower air pressure pocket right between the cans relative to the surrounding air. Because higher pressure pushes, the cans clink together. Just remember – whenever there’s a difference in pressure, the higher pressure pushes.

You will need about 25 straws and two empty soda cans or other lightweight containers

[am4show have=’p8;p9;p82;p84;p93;p30;p57;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Lay a row of straws parallel to each other on a smooth tabletop. Place two empty soda cans on the straws about an inch apart. Lower your nose to the cans and blow hard through the space between the two cans.

Clink! They should roll toward each other and touch!

[/am4show]

Going Further with Advanced Chemistry

Monday May 31, 2010

This experiment is for advanced students.

One of my best teaching tools for science developed from a brain freeze one afternoon in class. I went to the board to draw the chlorophyll wheel and drew a complete blank.

“Let’s say I forgot how to draw the wheel.” I turned to the class, marker in hand, and scanned the room. Puzzled faces, the blank faces I expected, but, what was that? A few smiles scattered about the room.

As I pulled out and some volunteered info, we got into that wheel. They also found that it was easier to know what to do next than to have me tell them to find it in their book and be prepared…I was coming back to them. Students frantically finding the wheel in their biology books so they were armed when I came to them.

It was a great experience, and my lectures were a lot more fun and interactive from then on.

[am4show have=’p9;p52;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Next, I started designing labs that way. Pre-reading was suggested, but they never read for homework…everybody knows that. But they soon found out why they should start reading ahead.

They came in for their lab.

There were a lot of lab supplies out on the counter. I had put all the supplies they would need on the counter. In addition, I put an equal number of supplies out that had nothing to do with the experiment. A problem was written at the top of the board such as, “We need to extract chlorophyll from the leaves on the counter.” And that was it. No lab book, they were on their own.

I gave a short lecture to bait their brains into remembering something and turned them loose. It took a couple of weeks, but I gained so much with them. Many more were reading at home to prepare for the lab, because they didn’t want to sit around trying to figure things out from scratch. They already had an idea on how to do the lab when they came on lab day. If they did not finish in the class time allotted, it was too bad. They could make up the lab later, but most just took the bad grade.

Many more students were motivated beyond my wildest expectations. Many students that were working hard to stay on the bottom started to feel a little peer pressure to help out. Students enjoyed the discovery…..they enjoyed the labs. No more cookie cutter labs for us.

Perhaps some labs in your curriculum could be designed to work this way as a way to provide more advanced learning in the sciences?

[/am4show]

Air Takes Space

Monday May 31, 2010

You’re about to play with one of the first methods of underwater breathing developed for scuba divers hundreds of years ago.! Back then, scientists would invert a very large clear, bell-shaped jar over a diver standing on a platform, then lower the whole thing into the water. Everyone thought this was a great idea, until the diver ran out of breathable air…

Materials: 12″ flexible tubing, two clear plastic cups, bathtub

[am4show have=’p8;p9;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Part I: Fill the tub and climb in. Plunge one cup underwater so it fills completely with water. While the cup is underwater, point its mouth downward. Insert one end of the tubing into the cup and blow hard into the other end. The water is forced out of the cup!

Part II: While still in the tub, invert one cup (mouth downwards) and plunge it into the tub so that air gets trapped inside the cup. Place the second cup in the water so it fills with water. Invert the water-filled cup while underwater and position it above the first cup so when you tilt the first cup to release the air bubbles, they get trapped inside the second cup. Here you see that air takes space, because in both variations of this experiment the air forced the water out of the cups.

[/am4show]

Solar Cookies

Saturday May 1, 2010

Can you use the power of the sun without using solar cells? You bet! We’re going to focus the incoming light down into a heat-absorbing box that will actually cook your food for you.

Remember from Unit 9 how we learned about photons (packets of light)? Sunlight at the Earth’s surface is mostly in the visible and near-infrared (IR) part of the spectrum, with a small part in the near-ultraviolet (UV). The UV light has more energy than the IR, although it’s the IR that you feel as heat.

We’re going to use both to bake cookies in our homemade solar oven. There are two different designs – one uses a pizza box and the other is more like a light funnel. Which one works best for you?

Two large sheets of poster board (black is best)
Aluminum foil
Plastic wrap
Black construction paper
Cardboard box
Pizza box (clean!)
Tape & scissors
Reusable plastic baggies
Cookie dough (your favorite)

[am4show have=’p8;p9;p22;p49;p75;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

How does that work? Your solar cooker does a few different things. First, it concentrates the sunlight into a smaller space using aluminum foil. This makes the energy from the sun more potent. If you used mirrors, it would work even better!

You’re also converting light into heat by using the black construction paper. If you’ve ever gotten into car with dark seats, you know that those seats can get HOT on summer days! The black color absorbs most of the sunlight and transforms it into heat (which boosts the efficiency of your solar oven).

By strapping on a plastic sheet over the top of the pizza-box cooker, you’re preventing the heat from escaping and cooling the oven off. Keeping the cover clear allows sunlight to enter and the heat to stay in. (Remember the black stuff converted your light into heat?) If you live in an area that’s cold or windy, you’ll find this part essential to cooking with your oven!

Here’s another type of solar cooker that uses a cone design to focus the energy straight to your cookies!

Exercises Answer the questions below:

Name the type of heat energy that the sun provides:
1. Convection
2. Conduction
3. Radiation
4. Invection
What are some ways that the sun’s energy can be directly harnessed?
Name three of the different parts of the electromagnetic spectrum:

[/am4show]

Solar Boat

Saturday May 1, 2010

Does it really matter what angle the solar cell makes with the incoming sunlight? If so, does it matter much? When the sun moves across the sky, solar cells on a house receive different amounts of sunlight. You’re going to find out exactly how much this varies by building your own solar boat.

We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) to build a solar-powered race car. You’ll need to find these items below. Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.

Solar motor
Solar cell
Foam block (about 6” long)
Alligator clip leads
Propeller (you can rip one off an old small personal fan or old toy, or find them at hobby stores)

Here’s what you do:

[am4show have=’p8;p9;p22;p49;p75;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

1. Attach the wires of the solar cell to the motor (one to each motor terminal).

2. Attach the propeller to your motor. If the shaft won’t fit, drill out the center hole. If the hole is too large, use a tiny dab of hot glue on the shaft tip to secure the propeller into place.

3. Stand out in the sun. How do you need to hold your solar cell to make the propellers pin the fastest?

4. Position the motor on a block of foam so that the propeller hangs off the edge and is free to rotate. Hot glue the motor into place, being careful not to get any hot glue near any vents in your motor.

5. Hot glue your solar cell to the foam block. You might want to check the final position in sunlight before attaching it.

6. Optional: Wire up a simple switch (from Unit 10) using paperclips and brass fasteners so you can easily turn your power on and off.

Going further: Using the same solar cell, you can also build a Wind Turbine and a Solar Car.

Exercises Answer the questions below:

What kind of electricity comes from a battery and photovoltaic cell?
1. Nuclear
2. Voltaic
3. Electrochemical
4. Ionized
Electricity is another name for the free flow of:
1. Protons
2. Quarks
3. Electrodes
4. Electrons
True or false: Ions are attracted to the same charge.
1. True
2. False
Do solar panels work in cloudy climates?
1. Yes
2. No

[/am4show]

Solar Car

Saturday May 1, 2010

Solar energy (power) refers to collecting this energy and storing it for another use, like driving a car. The sun blasts 174 x 1015 watts (which is 174,000,000,000,000,000 watts) of energy through radiation to the earth, but only 70% of that amount actually makes it to the surface. And since the surface of the earth is mostly water, both in ocean and cloud form, only a small fraction of the total amount makes it to land.

A solar cell converts sunlight straight into electricity. Most satellites are powered by large solar panel arrays in space, as sunlight is cheap and readily available out there. While solar cells seem ‘new’ and modern today, the first ones were created in the 1880s, but were a mere 1% efficient. (Today, they get as high as 35%.) A solar cell’s efficiency is a measure of how much sunlight the cell converts into electrical energy.

Solar cell
Solar motor
Foam block (about 6” long)
Alligator clip leads
2 straws (optional)
2 wooden skewers (optional)
4 milk jug lids or film can tops
Set of gears, one of which fits onto your motor shaft (most solar motor kits come with a set), or rip a set out of an old toy

Here’s what you do:

[am4show have=’p8;p9;p22;p49;p75;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

How does a solar cell work? Solar cells are usually made of silicon. Sunlight is made of packets of energy called photons (we covered this in Unit 9). When photons hit the silicon, one of three things can happen: the photons can pass straight through the silicon if they have a low enough energy; they can get reflected off the surface; or (and this is the fun part) they get absorbed and the electrons in the silicon get knocked out of their shell.

Once knocked out of orbit, the free electrons start flowing through the silicon to create electricity. The solar cells are structured is such a way as to keep the electricity flowing only in one direction. The electron flow created is DC current (refer to Unit 10).

The solar cells you can buy from stores require huge amounts of energy in creating the solar cell, which is the primary downside. You need high temperatures, big vacuum pumps, and lots of people to make a set of solar cells. However, if we focus just on the physics of the solar cell, then we can easily create our own solar battery and other solar cell projects using household items. While these cells won’t look as spiffy as the ones from the store, they still produce electricity from sunlight.

Using the same solar cell, you can also build a Wind Turbine and a Solar Boat.

Exercises Answer the questions below:

Most solar cells are made of what material?
1. Hydrogen
2. Aluminum
3. Silicon
4. Titanium
Name one benefit of solar cells and one drawback of using them for electricity.
1. Benefit:
2. Drawback:
Electrical current begins flowing when:
1. Sunlight hits an atom
2. Electrons are knocked out of orbiting atoms
3. Protons get charged
4. An atom’s nucleus splits

[/am4show]

Wind Turbine

Saturday May 1, 2010

Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Wind turbines spin big coils of wire around very powerful magnets (or very powerful magnets around big coils of wire) by capturing the flow.

Here’s how it works: when a propeller is placed in a moving fluid (like the water from your sink or wind from your hair dryer), the propeller turns. If you attach the propeller to a motor shaft, the motor will rotate, which has coils of wire and magnets inside. The faster the shaft turns, the more the magnets create an electrical current.

The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires! Refer to Unit 11 for more detail about how moving magnets create electricity.

We’re going to build a wind turbine that will actually give you different amounts of electricity depending on which way your propeller is facing. Ready?

You’ll need to find these items below. Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.

A digital Multimeter
Alligator clip leads
1.5-3V DC Motor
9-18VDC Motor
Bi-polar LED
Foam block (about 6” long)
Propeller from old toy or cheap fan, or balsa wood airplane

Here’s what you do:

[am4show have=’p8;p9;p22;p49;p85;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Using the same solar cell, you can also build a Solar Car and a Solar Boat.

Exercises

True or false: Electricity in a wind turbine is created by magnets in the turbine:
1. True
2. False
What is one advantage of using wind for electricity?
What might be one problem with constructing wind farms to meet all our energy needs?

[/am4show]

Marshmallow Roaster

Saturday May 1, 2010

Do you like marshmallows cooked over a campfire? What if you don’t have a campfire, though? We’ll solve that problem by building our own food roaster – you can roast hot dogs, marshmallows, anything you want. And it’s battery-free, as this device is powered by the sun.

NOTE: This roaster is powerful enough to start fires! Use with adult supervision and a fire extinguisher handy.

If you’re roasting marshmallows, remember that they are white – the most reflective color you can get. If you coat your marshmallows with something darker (chocolate, perhaps?), your marshmallow will absorb the incoming light instead of reflecting it.

Here’s what you need to get:

7×10” page magnifier (Fresnel lens)
Cardboard box, about a 10” cube
Aluminum foil
Hot glue, razor, scissors, tape
Wooden skewers (BBQ-style)
Chocolate, marshmallows, & graham crackers

Here’s what you do:

Download Student Worksheet & Exercises

How does it do that? The Fresnel lens is a lot like a magnifying glass. In Unit 9, we learned how convex lenses are thicker in the middle (you can feel it with your fingers). A Fresnel lens (first used in the 1800s to focus the beam in a lighthouse) has lots of ridges you can feel with your fingers. It’s basically a series of magnifying lenses stacked together in rings (like in a tree trunk) to magnify an image.

The best thing about Fresnel lenses is that they are lightweight, so they can be very large (which is why light houses used these designs). Fresnel lenses curve to keep the focus at the same point, no matter close your light source is.

The Fresnel lens in this project is focusing the incoming sunlight much more powerfully than a regular hand held magnifier. But focusing the light is only part of the story with your roaster. The other part is how your food cooks as the light hits it. If your food is light-colored, it’s going to cook slower than darker (or charred) food. Notice how the burnt spots on your food heat up more quickly!

Scientifically Dissecting a Marshmallow

Plants take in energy (from the sun), water, and carbon dioxide (which is carbon and oxygen) and create sugar, giving off the oxygen. In other words: carbon + water + energy = sugar

In this experiment, we will reverse this equation, by roasting a marshmallow, which is mostly sugar.
When you roast your marshmallow, first notice the black color. This is the carbon.
Next notice the heat and light given off. These are two forms of energy.
Finally, put the roasting marshmallow if a mason jar. Notice that condensation forms on the sides. This is the water.

So, by roasting the marshmallow, we showed: sugar = carbon + water + energy!

[am4show have=’p8;p9;p22;p49;p75;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
[/am4show]

Steamboats

Saturday May 1, 2010

In 1920’s, these were a big hit. They were originally called “Putt Putt Steam Boats”, and were fascinating toys for adults and kids alike. We’ll be making our own version that will chug along for hours. This is a classic demonstration for learning about heat, energy, and how to get your kids to take a bath.

Here’s what you need to build your own:

Copper tubing (1/8”-1/4” dia x 12” long)
Votive candle
Foam block
Scissors or razor (with adult help)
Bathtub

Here’s what you need to do:

Download Student Worksheet & Exercises

Wrap the copper tubing 2-3 times around a thick marker. You want to create a ‘coil’ with the tubing. Do this slowly so you don’t kink the tubing. End with two 3” parallel tails. (This is easier if you start in the middle of the tubing and work outwards in both directions.)
Stick each tail through a block of foam. Bend the wires to they run along the length of the bottom of the boat, slightly pointed upwards. (You can also use a plastic bottle cut in half.)
Position a votive candle on the topside of the boat and angle the coil so it sits right where the flame will be.
To start your boat, fill the bathtub with water. While your tub fills, hold the tubing in the running water and completely fill the coil with water.
Have your adult helper light the candle. In a moment, you should hear the ‘putt putt’ sounds of the boat working!
Troubleshooting: if your boat doesn’t work, it could be a few things:
1. The tubing has an air bubble. In this case, suck on one of the ends like a straw to draw in more water. Heating an air bubble will not make the boat move – it needs to be completely filled with water.
2. Your coil is not hot enough. You need the water to turn into steam, and in order for this to happen, you have to heat the coil as hot as you can. Move the coil into a better position to get heat from the flame.
3. The exhaust pipes are angled down. You want the stem to move up and out of your pipes, not get sucked back in. Adjust the exit tubing tails so they point slightly upwards.

How Do They Work? Your steam boat uses a votive candle as a heat source to heat the water inside the copper tubing (which is your boiling chamber). When the water is heated to steam, the steam pushes out the tube at the back with a small burst of energy, which pushes the boat forward.

Since your chamber is small, you only get a short ‘puff’ of energy. After the steam zips out, it creates a low pressure where it once was inside the tube, and this draws in fresh, cool water from the tub. The candle then heats this new water until steam and POP! it goes out the back, which in turn draws in more cool water to be heated… and on it goes. The ‘clicking’ or ‘putt putt’ noise you hear is the steam shooting out the back. This is go on until you either run out of water or heat.

Bonus! Here’s a video from a member that colored the water inside the pipe so they could see when it got pushed out! Note that the boat usually runs as fast as the first video on this page. The boats here are getting warmed up, ready to go, so they only do one or two puffs before they really start up.

Exercises Answer the questions below:

Name three sources of renewable or alternative energy:
Why is it important to look for renewable sources of energy?
What is one example of a fossil fuel?

[am4show have=’p8;p9;p22;p49;p85;’ guest_error=’Guest error message’ user_error=’User error message’ ]

[/am4show]

Solar Battery

Saturday May 1, 2010

This is the kind of energy most people think of when you mention ‘alternative energy’, and for good reason! Without the sun, none of anything you see around you could be here. Plants have known forever how to take the energy and turn it into usable stuff… so why can’t we?

The truth is that we can. While normally it takes factories the size of a city block to make a silicon solar cell, we’ll be making a copper solar cell after a quick trip to the hardware store. We’re going to modify the copper into a form that will allow it to react with sunlight the same way silicon does. The image shown here is the type of copper we’re going to make on the stovetop.

This solar cell is a real battery, and you’ll find that even in a dark room, you’ll be able to measure a tiny amount of current. However, even in bright sunlight, you’d need 80 million of these to light a regular incandescent bulb.

[am4show have=’p8;p9;p22;p49;p85;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]

You’ll need to gather these materials together:

½ sq. foot of copper flashing sheet (check the scrap bin at a hardware store)
Alligator clip leads
Multimeter
Electric stove (not gas)
Large plastic 2L soda bottle
¼ cup salt
Sandpaper & sheet metal shears

Here’s what you need to do:

Download Student Worksheet & Exercises

How does that work? Do you remember learning about the photoelectric effect in Unit 9? This cuprous oxide solar cell ejects electrons when placed in UV light – and sunlight has enough UV light to make this solar cell work. Those free electrons are now free to flow – which is exactly what we’re measuring with the volt meter.

Semiconductors are the secret to making solar cells. A semiconductor is a material that is part conductor, part insulator, meaning that electricity can flow freely and not, depending on how you structure it. There are lots of different kinds of semiconductors, including copper and silicon.

In semiconductors, there’s a gap (called the bandgap) that’s like a giant chasm between the free electrons (electrons knocked out of its shell) and bound electrons (electrons attached to an atom). Electrons can be either free or attached, but it costs a certain amount of energy to go either way (like a toll both).

When sunlight hits the semiconductor material in the solar cell, some of the electrons get enough energy to jump the gap and get knocked out of their shell to become free electrons. The free electrons zip through the material and create a low of electrons. When the sun goes down, there’s no source of energy for electrons to get knocked out of orbit, so they stay put until sunrise.

Exercises Answer the questions below:

The sunlight causes the electrons to flow from the cuprous oxide because of:
1. Photosynthesis
2. The electromagnetic spectrum
3. The photoelectric effect
4. The photochemical principle
What material do most solar cells use instead of copper?

What part of the electromagnetic spectrum is most active in this experiment?
1. Visible Light
2. Ultraviolet Light
3. Gamma Rays
4. Microwaves
When you read amps, you read:
1. Current
2. Voltage
3. Power Draw
4. Work

[/am4show]

Stirling Engine

Saturday May 1, 2010

This project is for advanced students.This Stirling Engine project is a very advanced project that requires skill, patience, and troubleshooting persistence in order to work right. Find yourself a seasoned Do-It-Yourself type of adult (someone who loves to fix things or tinker in the garage) before you start working on this project, or you’ll go crazy with nit-picky things that will keep the engine from operating correctly. This makes an excellent project for a weekend.

Developed in 1810s, this engine was widely used because it was quiet and could use almost anything as a heat source. This kind of heat engine squishes and expands air to do mechanical work. There’s a heat source (the candle) that adds energy to your system, and the result is your shaft spins (CD).

This engine converts the expansion and compression of gases into something that moves (the piston) and rotates (the crankshaft). Your car engine uses internal combustion to generate the expansion and compression cycles, whereas this heat engine has an external heat source.

This experiment is great for chemistry students learning about Charles’s Law, which is also known as the Law of Volumes, which describes how gases tend to expand when they are heated and can be mathematically written like this:

where V = volume, and T = temperature. So as temperature increases, volume also increases. In the experiment you’re about to do, you will see how heating the air causes the diaphragm to expand which turns the crank.

[am4show have=’p9;p49;p85;p88;p103;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

three soda cans
old inner tube from a bike wheel
super glue and instrant dry
electrical wire (3- conductor solid wire)
3 old CDs
one balloon
penny
nylon bushing (from hardware store)
alcohol burner (you can build one out of soda cans or Sterno canned heat)
fishing line (15lb. test or similar)
pack of steel wool
drill with 1/16″ bit
pliers
scissors
razor
wire cutters
electrical tape
push pin
permanent marker
Swiss army knife (with can opener option)
template
HINT: The “circle template” mentioned at 21:57 is actually just a circle traced from the bottom of the soda can onto a sheet of paper

The Stirling heat engine is very different from the engine in your car. When Robert Stirling invented the first Stirling engine in 1816, he thought it would be much more efficient than a gasoline or diesel engine. However, these heat engines are used only where quiet engines are required, such as in submarines or in generators for sailboats.

Download Student Worksheet & Exercises

Here’s how a Stirling engine is different from the internal-combustion engine inside your car. For example, the gases inside a Stirling engine never leave the engine because it’s an external combustion engine. This heat engine does not have exhaust valves as there are no explosions taking place, which is why Stirling engines are quieter. They use heat sources that are outside the engine, which opens up a wide range of possibilities from candles to solar energy to gasoline to the heat from your hand.

There are lots of different styles of Stirling engines. In this project, we’ll learn about the Stirling cycle and see how to build a simple heat engine out of soda cans. The main idea behind the Stirling engine is that a certain volume of gas remains inside the engine and gets heated and cooled, causing the crankshaft to turn. The gases never leave the container (remember – no exhaust valves!), so the gas is constantly changing temperature and pressure to do useful work. When the pressure increases, the temperature also increases. And when the temperature of the gases decreases, the pressure also goes down. (How pressure and temperature are linked together is called the “Ideal Gas Law”.)

Some Stirling engines have two pistons where one is heated by an external heat source like a candle and the other is cooled by external cooling like ice. Other displacer-type Stirling engines has one piston and a displacer. The displacer controls when the gas is heated and cooled.

In order to work, the heat engine needs a temperature difference between the top and bottom of the cylinder. Some Stirling engines are so sensitive that you can simply use the temperature difference between the air around you and the heat from your hand. Our Stirling engine uses temperature difference between the heat from a candle and ice water.

The balloon at the top of the soda can is actually the ‘power piston’ and is sealed to the can. It bulges up as the gas expands. The displacer is the steel wool in the engine which controls the temperature of the air and allows air to move between the heated and cooled sections of the engine.

When the displacer is near the top of the cylinder, most of the gas inside the engine is heated by the heat source and gas expands (the pressure builds inside the engine, forcing the balloon piston up). When the displacer is near the bottom of the cylinder, most of the gas inside the engine cools and contracts. (the pressure decreases and the balloon piston is allowed to contract).

Since the heat engine only makes power during the first part of the cycle, there’s only two ways to increase the power output: you can either increase the temperature of the gas (by using a hotter heat source), or by cooling the gases further by removing more heat (using something colder than ice).

Since the heat source is outside the cylinder, there’s a delay for the engine to respond to an increase or decrease in the heat or cooling source. If you use only water to cool your heat engine and suddenly pop an ice cube in the water, you’ll notice that it takes five to fifteen seconds to increase speed. The reason is because it takes time for the additional heat (or removal of heat by cooling) to make it through the cylinder walls and into the gas inside the engine. So Stirling engines can’t change the power output quickly. This would be a problem when getting on the freeway!

In recent years, scientists have looked to this engine again as a possibility, as gas and oil prices rise, and exhaust and pollutants are a concern for the environment. Since you can use nearly any heat source, it’s easy to pick one that has a low-fume output to power this engine. Scientists and engineers are working on a model that uses a Stirling engine in conjunction with an internal-combustion engine in a hybrid vehicle… maybe we’ll see these on the road someday!

Exercises

What is the primary input of energy for the Stirling engine?
As Pressure increases in a gas, what happens to temperature?
1. It increases
2. Nothing
3. It decreases
4. It increases, then decreases
What is the primary output of the Stirling engine?

[/am4show]

Galvanometers

Sunday April 4, 2010

Galvanometers are coils of wire connected to a battery. When current flows through the wire, it creates a magnetic field. Since the wire is bundled up, it multiplies this electromagnetic effect to create a simple electromagnet that you can detect with your compass.
[am4show have=’p8;p9;p21;p48;p106;p77;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Here’s what you need to do:

Materials:

magnet wire
sand paper
scissors
compass
AA battery case
2 AA batteries
2 alligator clip wires

Download Student Worksheet & Exercises

1. Remove the insulation from about an inch of each end of the wire. (Use sandpaper if you’re using magnet wire.)

2. Wrap the wire at least 30-50 times around your fingers, making sure your coil is large enough to slide the compass through.

3. Connect one end of the wire to the battery case wire.

4. While looking at the compass, repeatedly tap the other end of the wire to the battery. You should see the compass react to the tapping.

5. Switch the wires from one terminal of the battery to the other. Now tap again. Do you see a difference in the way the compass moves?

You just made a simple galvanometer. “Oh boy, that’s great! Hey Bob, take a look! I just made a….a what?!?” I thought you might ask that question. A galvanometer is a device that is used to find and measure electric current. “But, it made a compass needle move…isn’t that a magnetic field, not electricity?” Ah, yes, but hold on a minute. What is electric current…moving electrons. What do moving electrons create…a magnetic field! By the galvanometer detecting a change in the magnetic field, it is actually measuring electrical current! So, now that you’ve made one let’s use it!

More experiments with your galvanometer

You will need:

Your handy galvanometer
The strongest magnet you own
Another 2 feet or more of wire
Toilet paper or paper towel tube

1. Take your new piece of wire and remove about an inch of insulation from both ends of the wire.

2. Wrap this wire tightly and carefully around the end of the paper towel tube. Do as many wraps as you can while still leaving about 4 inches of wire on both sides of the coil. You may want to put a piece of tape on the coil to keep it from unwinding. Pull the coil from the paper towel tube, keeping the coil tightly wrapped.

3. Hook up your new coil with your galvanometer. One wire of the coil should be connected to one wire of the galvanometer and the other wire should be connected to the other end of the galvanometer.

4. Now move your magnet in and out of the the coil. Can you see the compass move? Does a stronger or weaker magnet make the compass move more? Does it matter how fast you move the magnet in and out of the coil?

Taa Daa!!! Ladies and gentlemen you just made electricity!!!!! You also just recreated one of the most important scientific discoveries of all time. One story about this discovery, goes like this:

A science teacher doing a demonstration for his students (can you see why I like this story) noticed that as he moved a magnet, he caused one of his instruments to register the flow of electricity. He experimented a bit further with this and noticed that a moving magnetic field can actually create electrical current. Thus tying the magnetism and the electricity together. Before that, they were seen as two completely different phenomena!

Now we know, that you can’t have an electric field without a magnetic field. You also cannot have a moving magnetic field, without causing electricity in objects that electrons can move in (like wires). Moving electrons create a magnetic field and moving magnetic fields can create electric currents.

“So, if I just made electricity, can I power a light bulb by moving a magnet around?” Yes, if you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet through the wire.

Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Electrical power plants either spin HUGE coils of wire around very powerful magnets or they spin very powerful magnets around HUGE coils of wire. The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires!

“But what about all those nuclear and coal power plants I hear about all the time?” Good question. Do you know what that nuclear and coal stuff does? It gets really hot. When it gets really hot, it boils water. When it boils water, it makes steam and do you know what the steam does? It causes giant wheels to turn. Guess what’s on those giant wheels. That’s right, a huge coil of wire or very powerful magnets! Coal and nuclear energy basically do little more than boil water. With the exception of solar energy almost all electrical production comes from something huge spinning really fast!

Exercises

Why didn’t the coil of wire work when it wasn’t hooked up to a battery? What does the battery do to the coil of wire?
How does a moving magnet make electricity?
What makes the compass needle deflect in the second coil?
Does a stronger or weaker magnet make the compass move more?
Does it matter how fast you move the magnet in and out of the coil?

[/am4show]

Which way is North?

Sunday April 4, 2010

I can still remember in 2nd grade science class wondering about this idea. And I still remember how baffled my teacher was when I asked her this question: “Doesn’t the north tip of a compass needle point to the south pole?” Think about this – if you hold up a magnet by a string, just like the needle of a compass, does the north end of the magnet line up with the north or south pole of the earth?

If you remember about magnets, you know that opposite attract. So the north tip of the compass will line up with the Earth’s SOUTH pole. So compasses are upside-down! Here’s an activity you can do right now…
Materials:

magnet
compass
string

[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

The magnetic pole which was attracted to the Earth’s north pole was labeled as the Boreal or “north-seeking pole” in the 1200s, which was later shortened to “north pole”. To add to the confusion, geologists call this pole the North Magnetic Pole.

Exercises

How are the lines of force different for the two magnets?
How far out (in inches measured from the magnet) does the magnet affect the compass?
What makes the compass move around?
Do you think the compass’s north–south indicator is flipped, or the Earth’s North Pole where the South Pole is? How do you know?

[/am4show]

Electromagnet

Sunday April 4, 2010

After you’ve completed the galvanometer experiment, try this one!

You can wrap wire around an iron core (like a nail), which will intensify the effect and magnetize the nail enough for you to pick up paperclips when it’s hooked up. See how many you can lift!

You can wrap the wire around your nail using a drill or by hand. In the picture to the left, there are two things wrong: you need way more wire than they have wrapped around that nail, and it does not need to be neat and tidy. So grab your spool and wrap as much as you can – the more turns you have around the nail, the stronger the magnet.

(We included this picture because there are so many like this in text books, and it’s quite misleading! This image is supposed to represent the thing you’re going to build, not be an actual photo of the finished product.)

Find these materials:

Batteries in a battery holder with alligator clip wires
A nail that can be picked up by a magnet
At least 3 feet of insulated wire (magnet wire works best but others will work okay)
Paper Clips
Masking Tape
Compass

[am4show have=’p8;p9;p21;p48;p106;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

1. Take your wire and remove about an inch of insulation from both ends. (Use sandpaper if you’re using magnet wire.)

2. Wrap your wire many, many times around the nail. The more times you wrap the wire, the stronger the electromagnet will be. Be sure to always wrap in the same direction. If you start wrapping clockwise, for example, be sure to keep wrapping clockwise.

3. Now connect one end of your wire to one terminal of the battery using an alligator clip (just like we did in the circuits from Unit 10).

4. Lastly, connect the other end of the wire to the other terminal of the battery using a second alligator clip lead to connect the electromagnet wire to the battery wire. This is where the wire may begin to heat up, so be careful.

5. Move your compass around your electromagnet. Does it affect the compass?

6. See if your electromagnet can pick up paper clips.

7. Switch the wires from one terminal of the battery to the other. Electricity is now moving in the opposite direction from the direction it was moving in before. Try the compass again. Do you see a change in which end of the nail the north side of the compass points to?

What happened there? By hooking that coil of wire up to the battery, you created an electromagnet. Remember, that moving electrons causes a magnetic field. Well, by connecting the two ends of your wire up to the battery, you caused the electrons in the wire to move through the wire in one direction.

Since many electrons are moving in one direction, you get a magnetic field! The nail helps to focus the field and strengthen it. In fact, if you could see the atoms inside the nail, you would be able to see them turn to align themselves with the magnetic field created by the electrons moving through the wire. You might want to test the nail by itself now that you’ve done the experiment. You may have caused it to become a permanent magnet!
[/am4show]

How Generators Work

Sunday April 4, 2010

Have you noticed that stuff sticks to your motor? If you drag your motor through a pile of paperclips, a few will get stuck to the side. What’s going on?

Inside your motor are permanent magnets (red and blue things in the photo) and an electromagnet (the copper thing wrapped around the middle). Normally, you’d hook up a battery to the two tabs (terminals) at the back of the motor, and your shaft would spin.

However, if you spin the motor shaft with your fingers, you’ll generate electricity at the terminals. But how is that possible? That’s what this experiment is all about.

[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

9-18V DC motor
LED (bi-polar)

If you move a magnet along the length of a wire, it will create a very faint bit of electricity inside the wire. If you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet past the wire.

A motor has a coil of wire wrapped around a central axis, so instead of rubbing back and forth (which is tough to going fast enough, because you have to stop, reverse direction, and start moving again every so often), it rotates past a set of magnets continuously.

When you add a battery pack to the motor terminals at the back, you energize the coil inside the motor, and it begins to rotate to attempt to line up its north and south poles. But the magnets are lined up in a way that it will continually ‘miss’ and overshoot, which keeps the shaft spinning over and over, faster and faster.

You can turn your motor into a generator by simply giving the shaft a quick spin with your fingers. Remember that attached to this shaft is a coil of wire. When you spin the shaft, you’re also moving a coil of wire past the permanent magnets inside to motor, which will create electricity in your coil and out the terminals.

You can attach a low-voltage LED directly to the motor terminals and spin the shaft to see the LED light up. Depending on the size of the magnets inside your motor, you may need to spin the shaft super fast to see the LED light up. The larger the motor, the easier this activity is. Try using a larger, 12V DC motor from the main shopping list for this section.

[/am4show]

Bouncing Magnets

Sunday April 4, 2010

Want to see a really neat way to get magnetic fields to interact with each other? While levitating objects is hard, bouncing them in invisible magnetic fields is easy. In this video, you’ll see how you can take two, three, or even four magnets and have them perform for you.

Are you ready?

Materials:

3 identical magnets

[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Did you notice that if the north pole of the bottom magnet is up, then the south pole of the magnet stacked above it will be down? The stack holds together because opposites attract (north-south). You probably already knew that, right? But notice when you pull the top magnet to the side the bottom south face is repelled into the air above the north face of the fixed magnet. So what gives?

Remember that a magnet isn’t strictly north or south. There are field lines that connect the two poles. The field lines start at one end and swoop down to the other and back again like in this picture to the left, reversing from north to south as it does so. This is why the south face is repelled – because it’s actually the magnetic fields that are doing the repelling.

You can adjust your two bouncing magnets to have nearly the same ‘bouncy’ (frequency) by changing their distance apart. Notice that when one magnet starts bouncing, the magnetic field changes, which pushes and pulls on the other magnet. The two magnets interact with each other through their magnetic fields, pushing and pulling each other into resonance.

British physicist Michael Faraday, famous for his many contributions to science including electrochemistry and electromagnetism.

Once you’ve mastered two magnets, why not try three? Or four? What happens when you bring a conductor, like a thick sheet of copper, aluminum (cookie sheet or cake pan) nearby? The eddy currents created in the metal by the moving magnet created an opposing magnetic field that work to ‘brake’ the moving magnet and stop it from bouncing.

While this activity may seem a bit trivial (and a little fun), the idea of a magnetic field is one of the greatest leaps ever made in science. Scientist Michael Faraday imagined the idea that a magnet had not only a magnetic field, but that it cold push and pull on other magnets and moving electric charges. This crazy idea was so wild that it took many scientists a lifetime to come to terms with it… as it replaced an older idea from Newton that had stood for centuries.

And, as usually happens when someone has a new bright idea, others are quick to add to it. Shortly after Faraday’s idea about magnetic fields and electrical charges, Maxwell combined complicated mathematics (stuff you’ll only see at a university) into his four famous equations (Maxwell’s Equations) that describe all electric and magnetic fields.

Exercises

Why does the magnet float?
After you tap the floating magnet, does it vibrate for a short or long time? Why?
Why do we stack the magnets first before trying to levitate them?
How many magnets can you get to interact while floating?
When you float two magnets above the main magnet, how do the floating magnets interact with each other? Why do they do that?

[/am4show]

Quick ‘n’ Easy DC Motor

Sunday April 4, 2010

Find a spare magnet – one you really don’t care about. Bring it up close to another magnet to find where the north and south poles are on the spare magnet. Did you find them? Mark the spots with a pen – put a N for north, and a S for south. Now break the spare magnet in half, separating the north from the south pole. (This might take a bit of muscle!) You should have one half be a north magnet, and the other a south. Or do you?

One of the big mysteries of the universe is why we can’t separate the north from the south end of a magnet. No matter how small you break that magnet down, you’ll still get one side that’s attracted to the north and the other that’s repelled. There’s just no way around this!

If you COULD separate the north from the south pole, you could point a magnet’s south pole toward your now-separated north pole, and it would always be repelled, no matter what orientation it rotated to. (Normally, as soon as the magnet is repelled, it twists around and lines up the opposite pole and snap! There go your fingers.) But if it were always repelled, you could chase it around the room or stick a pin through it so it would constantly move and rotate.

Well, what if we sneakily use electromagnetism? Note that you can use a metal screw, ball bearing, or other metal object that easily rotates. If your metal ball bearing is also magnetic, you can combine both the screw and the magnet together.

Famous scientist Michael Faraday built the first one of these while studying magnetic and electricity, and how they both fit together. What to see what he figured out?

Here’s what you do:

[am4show have=’p8;p9;p21;p48;p106;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

AA battery
small screw
wire (stripped on both ends)
very strong magnet (disc-shaped)

Download Student Worksheet & Exercises

Note: In case you missed it on the shopping list, you can order the disc magnet here.

The current from the battery is flowing through the wire, creating a magnetic field around the wire, which interacts with the magnetic field in the gold disk magnet. Since the wire creates a magnetic field that is perpendicular to the field in the gold magnet, the magnet feels a push, which causes it to rotate. Watch your fingers on this experiment – if you’re not careful and leave your wire contacting the magnet too long, you’ll roast your battery (and that’s really bad).

Exercises

How does this experiment work?
What happens if you reverse the polarity and attach the screw to the negative side of the battery?
How do you get your motor to spin the fastest?

[/am4show]

Magnetic Fields

Sunday April 4, 2010

This is a quick and simple experiment to answer the question of magnetic field strength: Do four magnets have a stronger magnetic pull than one? You’ll find the answer quite surprising… which is: it depends. Here’s what you need to do to see for yourself:

[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

stack of round magnets (7-9)
film canisters (or small containers like M&M containers)
clay or foam or tissue

Download Student Worksheet & Exercises

What’s going on here? When you bring the bottoms of the two film canisters together, you can feel the force of repulsion (if not, flip one of the stacks inside one of the the canisters). While you’ll definitely notice that the force of 4-on-4 magnets is larger than 1-on-1, you won’t be able to tell the difference between 4-on-1 or 1-on-4. Or, put more simply, you can’t tell which has one magnet and which has four. So what’s going on?

The more magnets you have, the more magnetic force they exert. The magnetic forces between two stacks of ten magnets magnets are equal and opposite. The magnetic force exerted by a stack of two magnets and five magnets is also equal and opposite, although somewhat less than the stack of ten.

It’s the same with gravity – the force of gravity between two masses (like the sun and the Earth) is also equal and opposite – or the earth would get pulled into the sun or go flying out of the solar system. The Earth exerts the same pull on the sun as the sun exerts on the Earth.

Say WHAT?!?

Did you expect four magnets to push with four times the force on the single magnet? That’s what common sense tells us. However, think of it this way: the 2nd, 3rd, and 4th magnets magnets are further away than the 1st magnet and so they each exert less and less of a push on the single magnet.

Exercises:

Why can’t you simply rub the needle back and forth with the magnet? Why do you have to stroke it in one direction?
What other objects/materials can you use to make a compass?
How do you know that the needle is magnetized?
Why did we float the needle in water?

[/am4show]

Relays & Homemade Shockers

Sunday April 4, 2010

This experiment is for advanced students. If you’ve attempted the relay and telegraph experiment, you already know it’s one of the hardest ones in this unit, as the gap needs to be *just right* in order for it to work. It’s a super-tricky experiment that can leave you frustrated and losing hope that you’ll ever get the hang of this magnetism thing.

Fear not, young scientist! Here’s a MUCH simpler relay experiment that will actually give a nice blue spark when fired up, along with a nice zap to the hand that touches it in just the right spot. You can also use this relay in your electricity experiments as a switch you can use to turn things on and off using electricity (instead of your fingers moving a switch), including how to make a latching burglar alarm circuit.

[am4show have=’p9;p48;p106;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

one relay
AA case
2 AA batteries
9V battery with clip (watch video)
alligator wires

Here’s what you need to do:

Download Student Worksheet & Exercises

Exercises

Is there a permanent magnet and/or an electromagnet inside a relay?
What makes the relay a switch?
What makes the relay turn on and off (*click*)?
Is the same power source that activates the relay also used for the circuit it’s switching?

[/am4show]

Magnetic Sensors

Sunday April 4, 2010

Wouldn’t it be cool to have an alarm sound each time someone opened your door, lunch box, or secret drawer? It’s easy when you use a reed switch in your circuit! All you need to do it substitute this sensor for the trip wire and you’ll have a magnetic burglar alarm.

The first thing you need to do is get your reed switch out, because we have to tear into it in order to get the part we need. Here’s what you need:

Materials:

reed switch
magnet
LED
AA case
2 alligator wires
2 AA batteries

[am4show have=’p8;p9;p21;p48;p108;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Download Student Worksheet & Exercises

Exercises

Where does the magnet need to be located in order for your circuit to work?
How does the switch work? Draw a picture and label the parts that make it work in the circuit.
Can the switch be activated through the side of a drawer, so that the switch is in the inside and the magnet is on the outside?
Which way does the magnet activate the switch the best? How are the poles oriented relative to the switch?

[/am4show]

Relays and Telegraphs

Sunday April 4, 2010

Relays are telegraphs, and they both are basically “electrical switches”. This means you can turn something on and off without touching it – you can use electricity to switch something else on or off!

We’re going to build our own relay that will attract a strip of metal to make our telegraph ‘click’ each time we energize the coil.

IMPORTANT! This experiment is very tricky to get working right. You’ll want to pair up with someone who’s handy in the workshop and has a keen eye and a feather touch for adjusting the clicker in the final step. Someone who is a patient, fix-it type of person will be able to help you get this project working well.

Note: There are bonus experiment ideas near the bottom once you’ve mastered this activity.

[am4show have=’p8;p9;p21;p48;p106;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

block of foam
sandpaper
alligator wires
battery case
AA batteries
film canister or similar
nail
thin magnet wire (26-28g)
brass fasteners
1/2″ strip from a soup can for the clicker (watch video)
paper clip
hot glue gun
scissors
tape

Download Student Worksheet & Exercises

1. Make the electromagnet first (the nail turns into a magnet when you add power to the wire): Carefully unwrap your wire and stretch it into a long length. Cut it roughly in half, reserving one half for the next experiment.

2. Wrap the thin insulated wire (called ‘magnet wire’) around the nail. (More wraps mean more power for your magnet, so use a lot!) You can insert a nail into a drill and wind it on slow speed, too. Sand the insulation off the end leads. (We do this so you can attach things to the exposed metal part.)

3. Insert the AA batteries into their case. Using alligator clips, clip onto a brass fastener and insert it into the foam.

4. Attach the other end of the clip lead to the positive battery terminal. Bend a paperclip into a “V” shape. Wind the free end of the exposed metal of the electromagnet wire around another brass fastener and insert through the tip of the “V” shape and into the foam, opened up on other side.

5. Be sure the smaller side of the “V” rests on the foam such that it does not reach the first brass fastener; but the larger side of the “V”, when pressed down, does. (You just made a switch!)

6. Stick the electromagnet pointy-end down into the foam. If it wiggles around, you will need to hot glue it into place later. Wiggling is good for now. Hot glue one end of the clicker (narrow steel strip) to the top of a film canister.

7. Attach the film canister with hot glue, making sure the tip of the clicker is over the nail head. Do not glue the lid to the canister! (It’s a big plus to have it rotate and be adjustable.) Be sure that the electromagnet and nail have a tiny clearance between the nail head and the metal strip. Push your switch to the “ON” position, and the electromagnet should click accordingly!

Troubleshooting: If it doesn’t click, move your electromagnet up or down, changing the nail-head-to-clicker distance until it clicks! If it sticks, it’s too close. If it doesn’t move at all, it’s too far away. Hot glue nail into right position. (Clicker is bendable, too—for future adjustments.)

Take your time – this is a project that requires patience and observation to figure out what’s going on. If you’re frustrated, STOP, try another experiment, and return back later. For a more permanent project, use a small block of wood instead of the foam and hammer in your nail.

Still struggling? Then click here to try an easier relay experiment with shocking results.

Why does this work? Anytime you run electricity through a wire, a magnetic field shows up. We’re multiplying this effect when we coil the wire around a nail. A nail with wire wrapped around it is called an electromagnet. Think of it like a magnet you can turn on and off.

Using a paper-clip switch, we can turn the electricity on and send it through the electromagnet, turning the ordinary nail and wire into a magnet. When we release the paper-clip switch, the current (electricity) stops flowing and our electromagnet turns back into ordinary nail and wire.

When the electromagnet is energized (magnetized), it attracts the metal strip, which causes it to click downwards. Release the paper-clip switch, and the strip is no longer attracted to the nail (because it’s no longer a magnet).

When the switch is on, it’s a magnet. When it’s off, it’s not a magnet. Magnets attract steel, and that’s why the strip bends and clicks. It’s amazing we could communicate over thousands of miles this way, but we did!

For Advanced Students Only!

If you’ve got the relay working and you want more… we’ve got one for you! Dual relays are often called “repeaters”. They take an incoming signal and “repeat” the signal and send it out. You’ll find uses for this when you want to increase the signal strength – you detect the weaker, older one and repeat out a newer, stronger signal identical to it. When radio signals need to traverse long distances, this is the basic idea of how they do it on high mountaintops.

Here’s how you can make your own:

1. Make a telegraph with a switch (previous experiment) first, then make a second telegraph, without the switch, on a new foam slab. Here’s what you do for the telegraph without the switch:

2. The second electromagnet uses the first relay as a switch. One end of the electromagnet goes to the negative battery terminal (don’t forget to sand the magnet wire first!).

3. Connect the positive wire lead to the first telegraph’s ‘clicker’ piece. Wrap it around securely. If it doesn’t stick, wrap the wire onto a paperclip then clip it to the clicker.

4. Connect the second (sanded) electromagnet wire to the first telegraph’s Nail. (It must touch the nail part, not the wire part, in order to work correctly!) Click the switch! The switch controls BOTH relays now. If you make the wires between the two foam slabs longer (say, 50 feet), you could relay messages back and forth!

Troubleshooting Relays: If a clicker doesn’t work, check the clearance. Move the electromagnet up and down, until you find the perfect clicking spot. It needs to be close enough to click, but far enough so it won’t stick.

Can you make several ‘repeaters’? Repeaters are telegraphs (relays) that get switched on by each other (after an initial input from you). Can you connect three or four telegraphs together so that they get switched on in sequence?

Exercises

Why does the soup can clicker move?
Does this circuit use a permanent or electromagnet?
Why do we need multiple turns around a nail? Why not just a couple wraps?
What is the paper-clip switch used for?
How can a relay be used in real life? Give three examples.

[/am4show]

Homemade DC Motor

Sunday April 4, 2010

Imagine you have two magnets. Glue one magnet on an imaginary record player (or a ‘lazy susan’ turntable) and hold the other magnet in your hand. What happens when you bring your hand close to the turntable magnet and bring the north sides together?

The magnet should repel and move, and since it’s on a turntable, it will circle out of the way. Now flip your hand over so you have the south facing the turntable. Notice how the turntable magnet is attracted to yours and rotates toward your hand. Just as it reaches your hand, flip it again to reveal the north side. Now the glued turntable magnet pushes away into another circle as you flip your magnet over again to attract it back to you. Imagine if you could time this well enough to get the turntable magnet to make a complete circle over and over again… that’s how a motor works!

This next activity mystifies even the most scientifically educated! Here’s what you need:

Materials:

magnet
magnet wire (26g works well)
D cell battery
two paper clips (try to find the ones shown in the video, or else bend your own with pliers)
sandpaper
fat rubber band

[am4show have=’p8;p9;p21;p48;p106;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

1. Start out by winding the magnet wire around a D-cell battery 12-15 times. Coil the wire around the circular loop to keep the wires together. Be sure that the “ears” are straight (see photo below). This is now your ‘rotor’:

2. IMPORTANT! Remove the insulation by sanding the entire length of both “ears”, flip the rotor over, and sand only one “ear” side, leaving the insulation intact on the side of the remaining “ear”.

3. Wrap the rubber band around the battery long-ways. Untwist a paper clip to make the shape shown in the video.

4. Make two of these paper clip shapes. You can use pliers to help make the shape. Place the left end under the rubber band in the center of the each end. The loop on the right end is where the rotor will hang (you can flip it over or bend accordingly if it falls out too much.)

5. Slide the rotor into the loops.

6. Place the magnet on the battery just under the rotor under the rubber band (you can use an additional rubber band to secure if needed). You want the rotor to be as close to the magnet as possible without hitting it. Give it a spin, and you’re off!

Troubleshooting: Usually problems arise when checking the connection between the battery and paper clips. Hold the battery with the fingertips in the center of each battery end and squeeze to make a good connection. If it still fails to spin, check your rotor: one ear should be insulation-free, the other should have a stripe of insulation down its length.

If you’re still having trouble, check the ears to be sure they are straight. The rotor needs to be able to spin nicely, so ensure it is well-balanced. Egg-shaped rotors just won’t turn.

Wow! How does THAT work? When you run electricity through any wire, it turns slightly into a magnet. When you stack wires on top of each other (as you did with the coil of wire), you multiply this effect and get a bigger magnet.

For the DC motor: The coil of wire is the O-shaped ring. When the sanded parts of the “ears” are connected to the paper clip, current flows through the circuit. When this happens, everything connects together and turns the coil wire into an electromagnet, which is then attracted to the magnet on the battery.

When the O-ring rotates, it moves around until the un-sanded portion breaks the connection and turns it back into just a coil of wire. The coil continues to float around in a circle until it hits the sanded parts again, which re-energizes the coil, turning it back into an electromagnet, which is now attracted to the magnet on the battery, which pulls it around again…and round it goes!

[/am4show]

Magnet Boats

Sunday April 4, 2010

We took our first step into the strange world of magnetism when we played with magnetizing a nail. We learned that magnets do what they do because of the behavior of electrons. When a bunch of those crazy little guys get going in the same direction they create a magnetic field. So what’s a magnetic field, you ask? That’s what this experiment is all about.

[am4show have=’p8;p9;p21;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

As the North and South sides of a magnet get closer together, the pull of the magnetic force is stronger. This is typical of fields. The closer you get, the stronger the pull of the force gets. The farther you get, the weaker the pull of the force gets.

Materials:

shallow dish or bathtub
water
foam blocks (or milk jug lids)
stack of 6-10 magnets
hot glue gun

Download Student Worksheet & Exercises

When you build the little boats, remember that you kept the poles all the same (all north pointed up, for example). The floating magnets repel each other because they have the same pole oriented up. But notice that when you bring the larger magnet close, they are all attracted to it and also make geometric patterns! When you bring the larger magnet in closer, the size of your pattern changes, doesn’t it? Most patterns have at least one (sometimes two) stable patterns, each of which is a local minimum energy pattern. The patterns that the little boats make are very similar to the crystal structures in solids.

Notice how the magnet boats repel each other when they get too close, yet the hold each other in a pattern. Atoms do the same thing – they repel each other when you try to squish them together, yet hold together to form molecules.

Exercises

What shape do three magnets give? Why is this different from the shape that four magnets make?
Why do the magnets flip over when you first place them in the water?
How many magnets make a hexagon?
How is this experiment like the compass experiments we’ve done so far?
Why do the boats repel each other, yet still hold in a pattern?

[/am4show]

Hearing Magnetism

Sunday April 4, 2010

Want to hear your magnets? We’re going to use electromagnetism to learn how you can listen to your physics lesson, and you’ll be surprised at how common this principle is in your everyday life. This project is for advanced students.

We’re going to invert the ideas used when we created our homemade speakers into a basic microphone. Although you won’t be able to record with this microphone, it will show you how the basics of a microphone and amplifier work, and how to turn sound waves back into electrical signals. You’ll be using the amplifier and your spare audio plug from the Laser Communicator for this project.

[am4show have=’p9;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

magnet wire
drill (or wind by hand)
nail
magnet
amplifier (see shopping list for info on where to get one)
audio plug

Download Student Worksheet & Exercises

An amplifier’s job is to take small electrical voltages (AKA the ‘input) and make them bigger (amplify them). Then, we usually plug a speaker or headphones into the amplifier and those turn the bigger electrical signal (AKA the ‘output’) into sound. So any small voltage that we plug into the amplifier’s input will get larger and then turn into sound through the built-in speaker.

One way to show this is to use a coil of wire and a magnet. If you take a coil of wire and move a magnet past, around, or through it, you will create a small electrical voltage (and current) in the wire. In fact, if you have enough wire and a big enough magnet, and move the magnet fast enough, the electricity coming out of the coil of wire can light up a light bulb (this is how an electric generator works).

So back to the amplifier: if we take the voltage from our little coil/magnet generator, and we put it into the amplifier, we’ll hear the sound from the speaker each time it makes a voltage. If we move the magnet back and forth really fast, we’ll hear a fast clicking sound. And if we were to move it super-incredibly-fast (faster than you could with your hands), then those clicks would blend together into a tone. Tones like this are what all sounds are made of.

In fact, this is exactly what a microphone does. Many microphones have a magnet and a coil of wire attached to a very thin piece of plastic or metal that vibrates when sound waves hit it. The plastic (or metal) in turn moves the coil of wire next to the magnet super-fast. Then this causes the electric voltage to come out of the coil and if you plug it into an amplifier it will make the same sound that the microphone heard, only louder.

Exercises

Why does the electromagnet make sound when you bring the permanent magnet close to it?
How is this like a microphone?
What did the aluminum do to the electromagnet?

[/am4show]

Rail Accelerator

Sunday April 4, 2010

We’re going to build on the quick ‘n’ easy DC motor to make a tiny rail accelerator (any larger, and you’ll need a power plant and a firing range and a healthy dose of ethics.) So let’s stick to the physics of what’s going on in this super-cool electromagnetism project. This project is for advanced students.

Here’s what we’re going to do:

We’re going to create two magnetic fields at right angles (perpendicular) to each other. When this happens, it causes things to move, spin, rotate, and roll out of the way. We’re going to focus this down to making a tiny set of wheel zip down a track powered only by magnetism. Ready?

[am4show have=’p9;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Materials:

cardboard
aluminum foil
hot glue
scissors
paper clip or wire coat hanger
two very small, strong disc magnets
9V battery with clip
2 alligator clip leads
pliers

Download Student Worksheet & Exercises

Did you notice how this rail accelerator is really just two of the ‘quick ‘n’ easy DC motors connected together? The wire is now the aluminum rail, and the magnetic field in the rail create a force perpendicular gold disk’s magnetic field. These two magnetic fields interact, causing the little wheels to roll. Which is why if you have the wheels on ‘backwards’ (or your battery connected backwards), your wheels will roll toward (instead of away) from you.

Troubleshooting: If you drop your wheels from too high up, you’ll knock the axle off-center and the wheels won’t roll. If your wheels still don’t roll, flip one of the magnets around (they must be in opposite directions for this to work!). Also make sure you’ve got a fresh 9V battery and good electrical connection between your clips and the track.

Exercises

Do the magnets need to be opposite in order for this to work?
Why do the wheels move?
Which track works the best?

[/am4show]

Curie Heat Engine

Sunday April 4, 2010

marie-curie — Marie Curie, a scientist famous for being the first person to receive two Nobel Prizes as well as her extensive work on radioactivity.

Magnetic material loses its ability to stick to a magnet when heated to a certain temperature called the Curie temperature. The Curie temperature for nickel is 380^oF, iron is 1,420^oF, cobalt is 2,070^oF, and for ceramic ferrite magnets, it starts at 860^oF.

We’re going to heat a magnet so that it loses temporarily loses its magnetic poles, and watch what happens as it cycles through cooling. Pierre and Marie Curie’s first scientific works were actually in magnetism, not chemistry, and their papers in magnetic fields and temperature when among the first noticed by the scientists at the time.

Are you ready to see what they figured out?

[am4show have=’p9;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:

large ceramic magnet
tiny bead magnet
copper wire
pen
candle (with adult help)
framework to hold the setup (watch video first)

Download Student Worksheet & Exercises

The Curie temperature for the ceramic magnet is much higher than a candle can produce, which is why the permanent magnet isn’t affected by the flame. The Curie temperature for the tiny bead magnet is around 600^oF, which is easily obtainable by your candle.

At the end of the swinging wire, there’s a tiny bead magnet, which is quite strong for its size. The magnet is attracted to the large ceramic magnet and moves toward it, almost touching it. The candle heats up the tiny bead magnet, causing it to temporarily lose its magnetism by adding energy into the atom and randomizing their orientation within the magnet. You’ll notice that the magnet quickly regains its magnetism after it cools. While you can permanently destroy the magnetic field in the bead magnet, you’d need something hotter than a propane torch to do it.

By the way, the Curie temperature for ceramic rare earth magnets is just under 600^oF, also within reach of your candle’s heat. The magnets are also on the small size, so they tend to heat up faster.

Exercises

Why does the tiny magnet lose its attraction to the large magnet?
How long does it take for the attraction-repulsion cycle to repeat?
Draw out your experiment, explaining how it works and labeling each part:

[/am4show]

Linear Accelerator

Sunday April 4, 2010

There are two ways to create a magnetic field. First, you can wrap wire around a nail and attach the ends of the wire to a battery to make an electromagnet. When you connect the battery to the wires, current begins to flow, creating a magnetic field. However, the magnets that stick to your fridge are neither moving nor plugged into the electrical outlet – which leads to the second way to make a magnetic field: by rubbing a nail with a magnet to line up the electron spin. You can essential “choreograph” the way an electron spins around the atom to increase the magnetic field of the material. This project is for advanced students.

There are several different types of magnets. Permanent magnets are materials that stay magnetized, no matter what you do to it… even if you whack it on the floor (which you can do with a magnetized nail to demagnetize it). You can temporarily magnetize certain materials, such as iron, nickel, and cobalt. And an electromagnet is basically a magnet that you can switch on and off and reverse the north and south poles.

The strength of a magnetic field is measured in “Gauss”. The Earth’s magnetic field measures 0.5 Gauss. Typical refrigerator magnets are 50 Gauss. Neodymium magnets (like the ones we’re going to use in this project) measure at 2,000 Gauss. The largest magnetic fields have been found around distant magnetars (neutron stars with extremely powerful magnetic fields), measuring at 10,000,000,000,000,000 Gauss. (A neutron star is what’s left over from certain types of supernovae, and typically the size of Manhattan.)

Linear accelerators (also known as a linac) use different methods to move particles to very high speeds. One way is through induction, which is basically a pulsed electromagnet. We’re going to use a slow input speed and super-strong magnets and multiply the effect to generate a high-speed ball bearing to shoot across the floor.

For this experiment, you will need:
[am4show have=’p9;p48;p77;’ guest_error=’Guest error message’ user_error=’User error message’ ]

• Wood or plastic ruler with a groove down the center
• Thick rubber bands or strong, super-sticky tape
• Four super-strong magnets (try 12mm or ½” neodymium magnets)
• Nine steel ball bearings (1/2”, 5/8”, or other sizes)

Here’s what you do:

Download Student Worksheet & Exercises

Question: Does it really matter where where you start the first ball bearing? If so, does it matter much?

What’s going on? The metal ball bearing is seriously attracted to your magnets, and this pull intensifies the closer the ball gets to the magnet (inverse-square law). When the ball smacks into the magnet, the energy wave from the impact zips through the magnet and attached ball bearings until it knocks the furthest ball free, which has the least magnetic pull on it (it’s furthest from the magnet)… which is good, or it would be slowed down and possible reattached to the magnet it just broke away from.

With each impact, there’s an increase in velocity. Imagine if you had a hundred of these things lined up… how fast could you get that last ball bearing going?

After each firing, you have to reset your system, and chances are, it takes a bit of effort to pull the ball bearings from the magnets! you are providing the energy that gets released during each collision and adds to the velocity of the ball bearings.

Want to turn this into a Science Fair Project? Click here for step-by-step instructions.

Exercises

Does it really matter where you start the first ball bearing? If so, does it matter much?
Why does only the last ball go flying away? Why don’t the others break away as well?
What happens if you try this experiment without the magnets?
How many inches did the first initial ball (the one you let go of) travel?
How many inches did the last ball (the one that detached from the magnet) travel?
Why did we use four magnets in the second lab? What did that do?

[/am4show]

Basic Circuits

Sunday March 7, 2010

An electrical circuit is like a raceway or running track at school. The electrons (racecars) zip around the race loop (wire circuit) superfast to make stuff happen. Although you can’t see the electrons zipping around the circuit, you can see the effects: lighting up LEDs, sounding buzzers, clicking relays, etc.

There are many different electrical components that make the electrons react in different ways, such as resistors (limit current), capacitors (collect a charge), transistors (gate for electrons), relays (electricity itself activates a switch), diodes (one-way street for electrons), solenoids (electrical magnet), switches (stoplight for electrons), and more. We’re going to use a combination diode-light-bulb (LED), buzzers, and motors in our circuits right now.

A CIRCUIT looks like a CIRCLE. When you connect the batteries to the LED with wire and make a circle, the LED lights up. If you break open the circle, electricity (current) doesn’t flow and the LED turns dark.

LED stands for “Light Emitting Diode”. Diodes are one-way streets for electricity – they allow electrons to flow one way but not the other.

Remember when you scuffed along the carpet? You gathered up an electric charge in your body. That charge was static until you zapped someone else. The movement of electric charge is called electric current, and is measured in amperes (A). When electric current passes through a material, it does it by electrical conduction. There are different kinds of conduction, such as metallic conduction, where electrons flow through a conductor (like metal) and electrolysis, where charged atoms (called ions) flow through liquids.

[am4show have='p8;p9;p20;p47;p106;p76;p97;p58;' guest_error='Guest error message' user_error='User error message' ]

Here's what you need:

2 AA heavy duty (carbon) batteries - Do not use alkaline or rechargeable batteries
AA battery case
2 alligator wires
LEDs (any you choose is fine)

Download Student Worksheet & Exercises

Be alert for:

1. Batteries inserted into the case the wrong way!

2. LED in the wrong way (LEDs are picky about plus and minus - they are POLARIZED)

3. Is there a metal-to-metal connection? (You're not grabbing ahold of the plastic insulation, are you?)

4. Bad wires can cause headaches - if all else fails, then swap out your alligator clip lead wires for new ones.

Exercises

What does LED stand for?
Does it matter which way you wire an LED in a circuit?
Does the longer wire on the LED connect to plus (red) or minus (black)?
Do you need to hook up batteries to make a neon bulb light up? Why or why not?
What's the difference between a light bulb and your LED?
What is the difference between a bolt of lightning and the electricity in your circuit?
What is the charge of an electron?

[/am4show]

Conductivity Testers

Sunday March 7, 2010

Make yourself a grab bag of fun things to test: copper pieces (nails or pipe pieces), zinc washers, pipe cleaners, Mylar, aluminum foil, pennies, nickels, keys, film canisters, paper clips, load stones (magnetic rock), other rocks, and just about anything else in the back of your desk drawer.

Certain materials conduct electricity better than others. Silver, for example, is one of the best electrical conductors on the planet, followed closely by copper and gold. Most scientists use gold contacts because, unlike silver and copper, gold does not tarnish (oxidize) as easily. Gold is a soft metal and wears away much more easily than others, but since most circuits are built for the short term (less than 50 years of use), the loss of material is unnoticeable.
[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Modify your basic LED circuit into a Conductivity Circuit by removing one clip lead from the battery and inserting a third clip lead to the battery terminal. The two free ends are your new clips to put things in from the grab bag. Try zippers, metal buttons, barrettes, water from a fountain, the fountain itself, bike racks, locks, doorknobs, unpainted benches… you get the idea!

Here’s what you need:

2 AA batteries
AA battery case
3 alligator wires
LEDs (any you choose is fine)
paper clip
penny
other metal objects around your house (zippers, chairs, etc…)

Why does metal conduct electricity?

Why does metal, not plastic, conduct electricity? Imagine you have a garden hose with water flowing through it. The hose is like the metal wire, and the water is like the electric current. Trying to run electricity through plastic is like filling your hose with cement. It’s just the nature of the material.

Download Student Worksheet & Exercises

Exercises

Name six materials that are electrically conductive.
What kinds of materials are conductors and insulators?
Can you convert an insulator into a conductor? How?
Name four instances when insulators are a bad idea to have around.
When are insulators essential to have?

[/am4show]

How to use a Digital MultiMeter

Sunday March 7, 2010

meter One of the most useful tools a scientist can have! A digital multimeter can quickly help you discover where the trouble is in your electrical circuits and eliminate the hassle of guesswork. When you have the right tool for the job, it makes your work a lot easier (think of trying to hammer nails with your shoe).

We'll show you how to get the most out of this versatile tool that we're sure you're going to use all the way through college. This project is for advanced students.

[am4show have='p9;p47;p107;p76;p58;' guest_error='Guest error message' user_error='User error message' ]

Download Student Worksheet & Exercises

Exercises

If you measure 2.65 volts from your battery pack, do you need new batteries or will they work?
How do you think you would measure the resistance of an LED?
Reset your meter for a quick practical test: Remove the wires from your DMM and set the dial at OFF. Wave your hand wildly and show how you can use the meter (you can add probes and turn it on now) to test the voltage on your LED in a simple circuit doing the steps from the experiment.

[/am4show]

Wiring Up Motors

Sunday March 7, 2010

After you get the buzzer and the light or LED to work, try spinning a DC motor:

[am4show have=’p8;p9;p20;p47;p106;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

2 AA batteries
AA battery case
2 alligator wires
1.5-3V DC motor
optional: propeller

[/am4show]

Pressure Sensor Burglar Alarm

Sunday March 7, 2010

By controlling how and when a circuit is triggered, you can easily turn a simple circuit into a burglar alarm – something that alerts you when something happens. By sensing light, movement, weight, liquids, even electric fields, you can trigger LEDs to light and buzzers to sound. Your room will never be the same.

Switches control the flow of electricity through a circuit. There are different kinds of switches. NC (normally closed) switches keep the current flowing until you engage the switch. The SPST and DPDT switches are NO (normally open) switches.

The pressure sensor we’re building is small, and it requires a fair amount of pressure to activate. Pressure is force (like weight) over a given area (like a footprint). If you weighed 200 pounds, and your footprint averaged 10” long and 2” wide, you’d exert about 5 psi (pounds per square inch) per foot.

However, if you walked around on stilts indeed of feet, and the ‘footprint’ of each stilt averaged 1” on each side, you’d now exert 100 psi per foot. Why such a difference?

The secret is in the area of the footprint. In our example, your foot is about 20 square inches, but the area of each stilt was only 1 square inch. Since you haven’t changed your weight, you’re still pushing down with 200 pounds, only in the second case, you’re pressing the same weight into a much smaller spot… and hence the pressure applied to the smaller area shoots up by a factor of 20.

So how do we use pressure in this experiment? When you squeeze the foam, the light bulb lights up! It’s ideal for under a doormat or carpet rug where lots of weight will trigger it.

[am4show have=’p8;p9;p20;p47;p108;p76;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Here’s what you need:

thin sponge or foam square (about 1″ square)
AA battery case
2 AA batteries
3 alligator clip wires
2 large paper clips
scissors
aluminum foil
buzzer or LED

Download Student Worksheet & Exercises

Troubleshooting: There are a few problem areas to watch out for when building this sensor. First, make sure the hole in your foam is big enough to stick a finger (or thumb) easily through. The foam keeps the foil apart until stepped on, then it squishes together to allow the foil to make contact through the hole.

The second potential problem is if the switch doesn’t turn the buzzer off. If this happens, it means you’re bypassing the switch entirely and keeping the circuit in the constant ON position. Check the two foil squares – are they touching around the outside edges? Lastly, make sure your foam is the kind that pops back into shape when released. (Thin sponges can work in a pinch.)

What’s happening? You’ve made a switch, only this one is triggered by squeezing it. If you’re using the special black foam without the hole, it works because the foam conducts more electricity when squished together, and less when it’s at the normal shape.

First, the special black foam is conducting some (but not enough) electricity when you squeeze it. It’s just the nature of the black foam included with the materials kit. Second, when you squeeze it, you’re getting the two foil squares to touch through the hole, and this is what really does it for your LED. When you release it, the foil spreads apart again because they are on opposite sides of the foam square.

Bonus Idea: Stick just the sensor under a rug and run longer wires from the sensor to your room. When someone comes down the hallway, they’ll trigger the sensor and alert you before they get there!

Exercises

How does this sensor work?
What makes this an NO switch?
How can you use both the trip wire and the pressure sensor in the same circuit? Draw it out here:

[/am4show]