Special Science Teleclass: Chemistry

Monday December 8, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too! (Click here if you’re looking for the more recent version that also includes Chemical Engineering.)


When you think of slime, do you imagine slugs, snails, and puppy kisses? Or does the science fiction film The Blob come to mind? Any way you picture it, slime is definitely slippery, slithery, and just plain icky — and a perfect forum for learning real science. But which ingredients work in making a truly slimy concoction, and why do they work? Let’s take a closer look…


Materials:


  • Sodium tetraborate (also called “Borax” – it’s a laundry whitener) – about 2 tablespoons
  • Clear glue or white glue (clear works better if you can find it) – about 1/2 cup
  • Yellow highlighter
  • Pliers or sharp razor (with adult help). (PREPARE: Use this to get the end off your highlighter before class starts so you can extract the ink-soaked felt inside. Leave the felt inside highlighter with the end loosely on (so it doesn’t dry out))
  • Resuable Instant Hand Warmer that contains sodium acetate (Brand Name: EZ Hand Warmer) – you’ll need two of these
  • Scissors
  • Glass half full of COLD water (PREPARE: put this in the fridge overnight)
  • Mixing bowl full of ice (PREPARE: leave in freezer)
  • Salt
  • Disposable aluminum pie place or foil-wrapped paper plate
  • Disposable cups for solutions (4-6)
  • Popsicle sticks for mixing (4-6)
  • Rubber gloves for your hands
  • Optional: If you want to see your experiments glow in the dark, you’ll need a fluorescent UV black light (about $10 from the pet store – look in cleaning supplies under “Urine-Off” for a fluorescent UV light). UV flashlights and UV LEDs will not work.

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Key Concepts

If you’ve ever mixed together cornstarch and water, you know that you can get it to be both a liquid and a solid at the same time. (If you haven’t you should definitely try it! Use a 2:1 ratio of cornstarch:water.) The long molecular chains (polymers) are all tangled up when you scrunch them together (and the thing feels solid), but the polymers are so slick that as soon as you release the tension, they slide free (and drips between your fingers like a liquid).


Scientists call this a non-Newtonian fluid. You can also fill an empty water bottle or a plastic test tube half-full with this stuff and cap it. Notice that when you shake it hard, the slime turns into a solid and doesn’t slosh around the tube. When you rotate the tube slowly, it acts like a liquid.


Long, spaghetti-like chains of molecules (called polymers) don’t clump together until you cross-link the molecule strands (polymers) together into something that looks more like a fishnet. This is how we’re going to make slime.


What’s Going On?

Imagine a plate of spaghetti. The noodles slide around and don’t clump together, just like the long chains of molecules (called polymers) that make up slime. They slide around without getting tangled up. The pasta by itself (fresh from the boiling water) doesn’t hold together until you put the sauce on. Slime works the same way. Long, spaghetti-like chains of molecules don’t clump together until you add the sauce – something to cross-link the molecule strands together.


The borax mixture holds the glue mixture together in a gloppy, gelatinous mass. In more scientific terms, the sodium tetraborate cross-links the long polymer chains in the glue to form the slime.


Why does the slime glow? Note that a black light emits high-energy UV light. You can’t see this part of the spectrum (just as you can’t see infrared light, found in the beam emitted from the remote control to the TV), which is why “black lights” were named that. Stuff glows because fluorescent objects absorb the UV light and then spit light back out almost instantaneously. Some of the energy gets lost during that process, which changes the wavelength of the light, which makes this light visible and causes the material to appear to glow.


Questions to Ask

  1. What happens when you freeze your slime? Is there a color change?
  2. How long does it take to thaw your slime in the microwave?
  3. Do you see the little bubbles in your slime?
  4. How many states of matter do you have in your slime now?
  5. Does this work with any laundry detergent, or just borax?
  6. What happens if you omit the water in the 50-50- glue-water mixture, and just use straight glue? (Hint – use the glow juice with the borax to keep the glowing feature.)
  7. Does your slime pick up newsprint from a newspaper?
  8. What other kinds of glue work well with this slime?

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Electrolysis

Saturday October 10, 2009

This experiment is just for advanced students. If you guessed that this has to do with electricity and chemistry, you’re right! But you might wonder how they work together. Back in 1800, William Nicholson and Johann Ritter were the first ones to split water into hydrogen and oxygen using electrolysis. (Soon afterward, Ritter went on to figure out electroplating.) They added energy in the form of an electric current into a cup of water and captured the bubbles forming into two separate cups, one for hydrogen and other for oxygen.

This experiment is not an easy one, so feel free to skip it if you need to. You don’t need to do this to get the concepts of this lesson but it’s such a neat and classical experiment (my students love it) so you can give it a try if you want to. The reason I like this is because what you are really doing in this experiment is ripping molecules apart and then later crashing them back together.

Have fun and please follow the directions carefully. This could be dangerous if you’re not careful. The image shown here is using graphite from two pencils sharpened on both ends, but the instructions below use wire.  Feel free to try both to see which types of electrodes provide the best results.

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You will need:

  • 2 test tubes or thin glass or plastic something closed at one end. I do not recommend anything wider than a half inch in diameter.
  • 2 two wires, one needs to be copper, at least 12 inches long. Both wires need to have bare ends.
  • 1 cup
  • sodium sulfate OR salt
  • Water
  • One 9 volt battery
  • Long match or a long thin piece of wood (like a popsicle stick) and a match
  • Rubber bands
  • Masking tape

Download Student Worksheet & Exercises
1. Fill the cup with water.

2. Put a tablespoon of salt or sodium sulfate into the water and stir it up. (The salt allows the electricity to flow better through the water.)

2. Put one wire into the test tube and rubber band it to the test tube so that it won’t come out (see picture).

3. Use the masking tape to attach both wires to the battery. Make sure the wire that is in the test tube is connected to the negative (-) pole of the battery and that the other is connected to the positive (+) pole. Don’t let the bare parts of the different wires touch. They could get very hot if they do.

4. Fill the test tube to the brim with the salt water.

5. This is the tricky part. Put your finger over the test tube, turn it over and put the test tube, open side down, into the cup of water. (See picture.)

6. Now put the other wire into the water. Be careful not to let the bare parts of the wires touch.

7. You should see bubbles rising into the test tube. If you don’t see bubbles, check the other wire. If bubbles are coming from the other wire either switch the wires on the battery connections or put the wire that is bubbling into the test tube and remove the other. If you see no bubbles check the connections on the battery.

8. When the test tube is half full of gas (half empty of salt water depending on how you look at it) light the long match or the wooden stick. Then take the test tube out of the water and let the water drain out. Holding the test tube with the open end down, wait for five seconds and put the burning stick deep into the test tube (the flame will probably go out but that’s okay). You should hear an instant pop and see a flash of light. If you don’t, light the stick again and try it another time. For some reason, it rarely works the first time but usually does the second or third.

A water molecule, as you saw before, is two hydrogen atoms and one oxygen atom. The electricity encouraged the oxygen to react with the copper wire leaving the hydrogen atoms with no oxygen atom to hang onto. The bubbles you saw were caused by the newly released hydrogen atoms floating through the test tube in the form of hydrogen gas. Eventually that test tube was part way filled with nothing but pure hydrogen gas.

But how do you know which bubbles are which? You can tell the difference between the two by the way they ignite (don’t’ worry – you’re only making a tiny bit of each one, so this experiment is completely safe to do with a grown up).

It takes energy to split a water molecule. (On the flip side, when you combine oxygen and hydrogen together, it makes water and a puff of energy. That’s what a fuel cell does.) Back to splitting the water molecule - as the electricity zips through your wires, the water molecule breaks apart into smaller pieces: hydrogen ions (positively charged hydrogen) and oxygen ions (negatively charged oxygen). Remember that a battery has a plus and a minus charge to it, and that positive and negative attract each other.

So, the positive hydrogen ions zip over to the negative terminal and form tiny bubbles right on the wire. Same thing happens on the positive battery wire. After a bit of time, the ions form a larger gas bubble. If you stick a cup over each wire, you can capture the bubbles and when you’re ready, ignite each to verify which is which.

If the match burns brighter, the gas is oxygen. If you hear a POP!, the gas is hydrogen. Oxygen itself is not flammable, so you need a fuel in addition to the oxygen for a flame. In one case, the fuel is hydrogen, and hence you hear a pop as it ignites. In the other case, the fuel is the match itself, and the flame glows brighter with the addition of more oxygen.

When you put the match to it, the energy of the heat causes the hydrogen to react with the oxygen in the air and “POP”, hydrogen and oxygen combine to form what? That’s right, more water. You have destroyed and created water! (It’s a very small amount of water so you probably won’t see much change in the test tube.)

The chemical equations going on during this electrolysis process look like this:

A reduction reaction is happening at the negatively charged cathode. Electrons from the cathode are sticking to the hydrogen cations to form hydrogen gas:

2 H+(aq) + 2e- --> H2(g)

2 H2O(l) + 2e- --> H2(g) + 2 OH-(aq)

The oxidation reaction is occurring at the positively charged anode as oxygen is being generated:

2 H2O(l)  --> O2(g) + 4 H+(aq) + 4e-

4 OH-(aq) --> O2(g) + 2 H2O(l) + 4 e-

Overall reaction:

2 H2O(l)  --> 2 H2(g) + O2(g)

Note that this reaction creates twice the amount of hydrogen than oxygen molecules. If the temperature and pressure for both are the same, you can expect to get twice the volume of hydrogen to oxygen gas (This relationship between pressure, temperature, and volume is the Ideal Gas Law principle.)

This is the idea behind vehicles that run on sunlight and water.  They use a solar panel (instead of a 9V battery) to break apart the hydrogen and oxygen and store them in separate tanks, then run them both back together through a fuel cell, which captures the energy (released when the hydrogen and oxygen recombine into water) and turns the car's motor. Cool, isn't it?

Note: We're going to focus on Alternative Energy in Unit 12 and create all sorts of various energy sources including how to make your own solar battery, heat engine, solar & fuel cell vehicles (as described above), and more!

Exercises

  1. Why are bubbles forming?
  2. Did bubbles form at both wires, or only one? What kind of bubbles are they?
  3. What would happen if you did this experiment with plain water? Would it work? Why or why not?
  4. Which terminal (positive or negative) produced the hydrogen gas?
  5. Did the reaction create more hydrogen or more oxygen?

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The Breaking Point

Sunday October 4, 2009
If you've ever teetered on the edge of a diving board, you know that the board flexes under your weight.  The heavier you are, the more it bends.  The top of the board gets slightly stretched further than the normal length (tension) while the underside gets slightly shorter (compressed). We're going to duplicate this without needing to visit the pool.

We're going to expand on the topic covered in the Tension and Compression section of this article. All you need for this experiment is:
  • a pencil or a craft stick that you don’t mind breaking
  • a pair of hands
[am4show have='p8;p9;p13;p40;' guest_error='Guest error message' user_error='User error message' ] 1. Grab the pencil or the craft stick with one hand on one end of the object and the other hand on the opposite end.

2. Bend the pencil or craft stick a bit, but not too far....yet. Notice how you can bend it quite a bit without it breaking.

3. Now, feel free to bend it slowly until it breaks.



Download Student Worksheet

You have just played with tension, compression and elasticity. When you bent the pencil it had no problem going back to its original shape right? Wood is fairly elastic, meaning it can bend quite a bit before breaking. This comes in quite handy if you happen to be a tree, since you can bend in the wind which allows you to survive most storms without breaking.

Now, let’s look at tension and compression. If you look at the pencil or craft stick that you just broke you may notice that one side of the break may look different then the other side. Tension is when things get pulled apart. Compression is when things get squashed together.

If you bent your pencil towards the ground for example, the molecules along the top of the pencil were pulled apart, and the molecules along the bottom were squashed together. If you didn’t bend too far they just went back to normal when you stopped applying force. However if you bent too far, “SNAP”, the pencil broke in two! Just like objects have an elastic limit that if you go beyond it you will break it, things also have a tension and compression limit. Pull something or push something too far, and you’ll break it. [/am4show]

Moon Sand

Sunday October 4, 2009

A non-Newtonian fluid is a substance that changes viscosity, such as ketchup.  Ever notice how ketchup sticks to the bottom of the bottle one minute and comes sliding out the next?


Think of viscosity as the resistance stuff has to being smeared around.   Water is “thin” (low viscosity); honey is “thick” (high viscosity).  You are about to make a substance that is both (low and high viscosity), depending on what ratio you mix up. Feel free to mix up a larger batch then indicated in the video – we’ve heard from families that have mixed up an entire kiddie pool of this stuff!


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  • cornstarch (about 2 cups)
  • water (about 1 cup)
  • sand (about 2 cups)

Your first step is to create a 2:1 ratio of cornstarch to water (2 cups cornstarch to 1 cup water).  (This is your non-Newtonian fluid.)  Grab it with your fist and it will turn rock-solid and crumble; open your hand and it will flow right between your fingers. It’s both a solid and a liquid (it changes viscosity depending on its environment, which is your hand right now).  By adding sand to this concoction, you can make moon sand.



 
Download Student Worksheet & Exercises


Moon sand is basically clay with a beach twist.  If you’ve ever tried making a sand castle, you know the disappointment of having the structure crumble after hours of work.  Moon sand adds the best properties of clay to the sand for a moldable, sandy texture that’s easy to work with — and it’s dirt cheap to mix up your weight in moon sand.


Your task is to find the perfect ratio of the three ingredients to make this weird substance.  If you have too much water, you’ll get a substance that is both a liquid and a solid (as you did before with the non-Newtonian fluid).  Too much solid, and it crumbles.


Troubleshooting: The smaller the grain of sand you have, the easier it is to form intricate shapes.  If you find white sand, it’ll make better colors when you add food dye to the mixture. Use a large enough bowl and try to keep one hand clean so you can add more (of whatever you need) as you go along.  The ideal mixture is approximately 2 cups sand, 2 cups cornstarch, and 1 cup water, give or take a bit.  Notice how adding just a small amount of water turns it into a liquid, and adding a tiny bit more cornstarch (or sand) makes it crumble as if it were solid?  Take your time to get this mixture just right. (We’ve filled up an entire plastic kiddie pool with this stuff!)
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Lesson 2: Solids (Video)

Friday October 2, 2009

Now, that you’ve spent some quality time with atoms and that wacky electron fellow you have a bit of an understanding of what is inside everything. The next thing you need to know is…what’s everything?



Lesson 1: Atoms & Density (Video)

Friday October 2, 2009

We’re going to study atoms, their parts, as well as how they work together. Are you ready? You can get started by watching this video:


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Microwaving Soap

Friday October 2, 2009

soapWhen you warm up leftovers, have you ever wondered why the microwave heats the food and not the plate? (Well, some plates, anyway.) It has to do with the way microwaves work.


Microwaves generate high energy electromagnetic waves that when aimed at water molecules, makes these molecules get super-excited and start bouncing around a lot.


We see this happen when we heat water in a pot on the stove. When you add energy to the pot (by turning on the stove), the water molecules start vibrating and moving around faster and faster the more heat you add. Eventually, when the pot of water boils, the top layer of molecules are so excited they vibrate free and float up as steam.


When you add more energy to the water molecule, either by using your stove top or your nearest microwave,  you cause those water molecules to vibrate faster. We detect these faster vibrations by measuring an increase in the temperature of the water molecules (or in the food containing water). Which is why it’s dangerous to heat anything not containing water in your microwave, as there’s nowhere for that energy to go, since the electromagnetic radiation is tuned to excite water molecules.


To explain this to younger kids (who might confuse radio waves with sounds waves) you might try this:


There’s light everywhere, some of which you can see (like rainbows) and others that you can’t see (like the infrared beam coming from your TV remote, or the UV rays from the sun that give you a sunburn). The microwave shoots invisible light beams at your food that are tuned to heat up the water molecule.


The microwave radiation emitted by the microwave oven can also excite other polarized molecules in addition to the water molecule, which is why some plates also get hot. The soap in this experiment below will show you how a bar of Ivory soap contains air, and that air contains water vapor which will get heated by the microwave radiation and expand. Are you ready?


Here’s what you need:


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  • bar of Ivory soap
  • microwave (not a new or expensive one)
  • plate (optional)

The following experiment is a quick example of this principle using a naked bar of Ivory soap. The trick is to use Ivory, which contains an unusually high amount of air. Since air contains water moisture, Ivory also has water hidden inside the bar of soap. The microwave will excite the water molecules and your kids will never look at the soap the same way again.



 
Download Student Worksheet & Exercises


Toss a naked bar of Ivory soap onto a glass or ceramic plate and stick it into the microwave (don’t use a new or expensive microwave!) on HIGH for 2-3 minutes. Watch intently and remove when it reaches a “maximum”. Be careful when you touch it after taking it out of the microwave oven – it may still hold steam inside. You can still use the soap and the microwave after this experiment!


Note: Scientists refer to ‘light’ as the visible part of the electromagnetic spectrum, where radio and microwaves are lower energy and frequency than light (and the height of the wave can be the size of a football field). Gamma rays and x-rays are higher energy and frequency than light (these tend to pass through mirrors rather than bounce off them. More on that in Unit 9.)


Exercises


  1.  What is it in your food (and the soap) that is actually heated by the microwave?
  2.  How does a microwave heat things?
  3.  Touch the soap after it has been allowed to cool for a few minutes and record your observations.

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Rock Candy Crystals

Friday October 2, 2009

Crystals are formed when atoms line up in patterns and solidify.  There are crystals everywhere — in the form of salt, sugar, sand, diamonds, quartz, and many more!


To make crystals, you need to make a very special kind of solution called a supersaturated solid solution.  Here’s what that means: if you add salt by the spoonful to a cup of water, you’ll reach a point where the salt doesn’t disappear (dissolve) anymore and forms a lump at the bottom of the glass.


The point at which it begins to form a lump is just past the point of saturation. If you heat up the saltwater, the lump disappears.  You can now add more and more salt, until it can’t take any more (you’ll see another lump starting to form at the bottom).  This is now a supersaturated solid solution.  Mix in a bit of water to make the lump disappear.  Your solution is ready for making crystals.  But how?


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Here’s what you need:


  • pencil or wooden skewer
  • string
  • glass jar (cleaned out pickle, jam or may jars work great)
  • 8 cups of sugar
  • 3 cups water
  • paper clip
  • adult help and a stove
  • food coloring  is optional but fun!

If you add something for the crystals to cling to, like a rock or a stick, crystals can grow.  If you “seed” the object (coat it with the stuff you formed the solution with, such as salt or sugar), they will start forming faster. If you have too much salt (or other solid) mixed in, your solution will crystallize all at the same time and you’ll get a huge rock that you can’t pull out of the jar.  If you have too little salt, then you’ll wait forever for crystals to grow. Finding the right amount takes time and patience.



 
Download Student Worksheet & Exercises


1. If you plan on eating the sugar crystal when you’re done you probably want to boil water with the jar and the paper clip in it to get rid of any nasties. Be careful, and don’t touch them while they are hot.


2. Tie one end of the string to the pencil and the opposite end to the paper clip.  (You can alternatively use a skewer instead of a piece of string to make it look more like the picture above, but you’ll need to figure out a way to suspend the skewer in the jar without touching the sides or bottom of the jar.)


3. Wet the string a bit and roll it in some sugar. This will help give the sugar crystals a place to start.


4. Place the pencil across the top of the jar. Make sure the clip is at the bottom of the jar and that the string hangs straight down into the jar. Try not to let the sting touch the side of the jar.


5. Heat 3 cups of water to a boil


6. Dissolve 8 cups of sugar in the boiling water (again be careful!). Stir as you add. You should be able to get all the sugar to dissolve. You can add more sugar until you start to see undissolved bits at the bottom of the pan.  If this happens, just add a bit of water until they disappear.


7. Feel free to add some food coloring to the water.


rockcandy8. Pour the sugar water into the jar. Put the whole thing aside in a quiet place for 2 days to a week. You may want to cover the jar with a paper towel to keep dust from getting in.


You should see crystals start to grow in about 2 days. They should get bigger and bigger over the few days. Once you’re happy with how big your crystals get, you can eat them! It’s nothing but sugar! (Be sure to brush your teeth!)  This one (left) us about 6 months old.


There you go! Next time you hold a pencil, throw a ball, or put on a shoe try to keep in mind that what you’re doing is using an object that is made of tiny strange atoms all held tightly together by their bonds.


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Penny Crystal Structure

Friday October 2, 2009

penny-structureThe atoms in a solid, as we mentioned before, are usually held close to one another and tightly together. Imagine a bunch of folks all stuck to one another with glue. Each person can wiggle and jiggle but they can’t really move anywhere.


Atoms in a solid are the same way. Each atom can wiggle and jiggle but they are stuck together. In science, we say that the molecules have strong bonds between them. Bonds are a way of describing how atoms and molecules are stuck together.


There’s nothing physical that actually holds them together (like a tiny rope or something). Like the Earth and Moon are stuck together by gravity forces, atoms and molecules are held together by nuclear and electromagnetic forces. Since the atoms and molecules come so close together they will often form crystals.


Try this experiment and then we will talk more about this:
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Here’s what you need:


  • 50 pennies
  • ruler


 
Download worksheet and exercises


Lay about 20-50 pennies on the table so that they are all sitting flat on the table. Now, use the ruler (or your hand) to push the pennies toward one another so that you have one big glob of pennies on the table all touching one another. Don’t push so hard that they pile on top of one another. Just get one nice big flat blob of pennies.


Pretty simple huh? However, take a look at the pennies, do you notice anything? You may notice that the pennies form patterns. How could that happen? You just shoved them together you didn’t lay them out in any order. Taa daa! That’s what often happens when solids form.


The molecules are pulled so close to one another that they will form patterns, also known as matrices. These patterns are very dependent on the shape of the molecule so different molecules have a tendency to form different shaped crystals. Salt has a tendency to be “cubey”. Go take a look… and you’ll find that they are like little blocks!


Water has a tendency to from triangle or hexagon shapes which is why snowflakes have six sides. Your pennies also form a hexagon shape. Solids don’t always form crystals but they are more common than you might think. A solid that’s not in a crystalline form is called amorphous. Before you put your pennies away I want you to notice one more thing.


Here’s what you do:


1. Take your pennies and lay them flat on the table.


2. Push them together so they all touch without overlapping.


3. Place your ruler on the right hand side of your penny blob so that it’s touching the bottom half of your pennies.


4. Slowly push the ruler to the left and watch the pennies.


You may have noticed that the penny “crystal” split in quite a straight line. This is called cleavage. Since crystals form patterns the way they do they will tend to break in pretty much the same way you saw your pennies break.


Break an ice cube and take a look. You may see many straight sections. This is because the ice molecules “cleave” according to how they formed. The reason you can write with a pencil is due to this concept. The pencil is formed of graphite crystal. The graphite crystal cleaves fairly easily and allows you to write down your amazing physics discoveries!


(The image here is a graphite crystal.) [/am4show]


Laundry Soap Crystals

Friday October 2, 2009

Can we really make crystals out of soap?  You bet!  These crystals grow really fast, provided your solution is properly saturated.  In only 12 hours, you should have sizable crystals sprouting up.


You can do this experiment with either skewers, string, or pipe cleaners.  The advantage of using pipe cleaners is that you can twist the pipe cleaners together into interesting shapes, such as a snowflake or other design.  (Make sure the shape fits inside your jar.)


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Here’s what you need:


  • pipe cleaners (or string or skewer)
  • cleaned out pickle, jam, or mayo jar
  • water
  • borax (AKA sodium tetraborate)
  • adult help, stove, pan, and stirring spoon

Here’s what you do:


1. Cut a length of string and tie it to your pipe cleaner shape; tie the other end around a pencil or wooden skewer. You want the shape suspended in the jar, not touching the bottom or sides.


2. Bring enough water to fill the jar (at least 2 cups) to a boil on the stove (food coloring is fun, but entirely optional).


3. Add 1 cup of borax (aka sodium tetraborate or sodium borate) to the solution, stirring to dissolve. If there are no bits settling to the bottom, add another spoonful and stir until you cannot dissolve any more borax into the solution. When you see bits of borax at the bottom, you’re ready.  (You’ll be adding in a lot of borax, which is why we asked you to get a full box). You have made a supersaturated solution.  Make sure your solution is saturated, or your crystals will not grow.


4. Wait until your solution has cooled to about 130oF (hot to the touch, but not so hot that you yank your hand away). Pour this solution (just the liquid, not the solid bits) into the jar with the shape.  Put the jar in a place where the crystals can grow undisturbed overnight, or even for a few days.  Warmer locations (such as upstairs or on top shelves) is best.



Download worksheet and exercises


DO  NOT EAT!!! Keep these crystals out of reach of small kids, as they look a lot like the Rock Candy Crystals.


Here are photos from kids ages 2, 7, 9 that made their own! Great job to the Fluker Family!!


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Plasma Grape

Friday October 2, 2009

CAUTION!! Be careful with this!! This experiment uses a knife AND a microwave, so you’re playing with things that slice and gets things hot. If you’re not careful you could cut yourself or burn yourself. Please use care!


We’re going to create the fourth state of matter in your microwave using food.  Note – this is NOT the kind of plasma doctors talk about that’s associated with blood.  These are two entirely different things that just happen to have the same name.  It’s like the word ‘trunk’, which could be either the storage compartment of a car or an elephant’s nose.  Make sense?


Plasma is what happens when you add enough energy (often in the form of raising the temperature) to a gas so that the electrons break free and start zinging around on their own.  Since electrons have a negative charge, having a bunch of free-riding electrons causes the gas to become electrically charged.  This gives some cool properties to the gas.  Anytime you have charged particles (like naked electrons) off on their own, they are referred to by scientists as ions.  Hopefully this makes the dry textbook definition make more sense now (“Plasma is an ionized gas.”)


So here’s what you need:


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  • microwave (not a new or expensive one)
  • a grape
  • a knife with adult help


 
Download Student Worksheet & Exercises


1. Carefully cut the grape almost in half. You want to leave a bit of skin connecting the two halves.


2. Open the grape like a book. In other words, so that the two halves are next to one another still attached by the skin.


3. Put the grape into the microwave with the outside part of the grape facing down and the inside part facing up.


4. Close the door and set the microwave for ten seconds. You may want to dim the lights in the room.


s2You should see a bluish or yellowish light coming from the middle section of the grape. This is plasma! Be careful not to overcook the grape. It will smoke and stink if you let it overcook. Also, make sure the grape has time to cool before taking it out of the microwave.


Other places you can find plasma include neon signs, fluorescent lights, plasma globes, and small traces of it are found in a flame.


Note: This experiment creates a momentary, high-amp short-circuit in the oven, a lot like shorting your stereo with low-resistance speakers. It’s not good to operate a microwave for long periods with little to nothing in them.  This is why we only do it for a few seconds. While this normally isn’t a problem in most microwaves, don’t do this experiment with an expensive microwave or one that’s had consistent problems, as this might push it over the edge.


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Pile It In

Friday October 2, 2009

emperorpenguinsDensity is basically how tightly packed atoms are. Mathematically, density is mass/volume. In other words, it is how heavy something is, divided by how much space it takes up. If you think about atoms as marbles (which we know they’re not from the last lessons but it’s a useful model), then something is more dense if its marbles are jammed close together.


For example, take a golf ball and a ping pong ball. Both are about the same size or, in other words, take up the same volume. However, one is much heavier, has more mass, than the other. The golf ball has its atoms much more closely packed together than the ping pong ball and as such the golf ball is denser.


This experiment builds on the Play With Your Food experiment, so we’ll be learning more about density.  Are you ready?


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Gather your materials:


  • small paper cups
  • a scale that measures small masses (a kitchen scale is good)
  • bunches of different small stuff (pennies, cereal, marbles, etc.)
  • a little water and/or other liquids (milk, syrup, etc.)
  • pencil, paper
  • measuring cup (optional)
  • container that’s larger and deeper then the small paper cup (optional)

1. Put a line with a pencil on the inside and on the outside of the paper cup about half an inch (centimeter) from the top.


2. Fill the cup to the line with whatever kind of stuff you’re using.


3. Weigh the cup and record its mass.


4. Empty the cup and fill it with something else. Record its mass as well.


5. Continue until you’ve done at least five different masses.


For advanced students:

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The following steps are optional. They will help you find out the volume of the materials you’re using. I recommend doing this only if the math won’t turn you off to the concept.


6. Take your larger container, fill it to the brim and place it into your bowl.


7. Take your paper cup and push it into the larger container. Push it in until it reaches the line on the outside of your cup. You should have water coming out of your glass and going into your bowl. Pull the paper cup out of the container and pull the container out of the bowl.


8. Take the water in the bowl and pour it into the measuring cup. Write down the measurement. This is the volume of the cup. Since you are using the same volume for each measurement, (you’re filling the cup to the same line each time) you only need to do this once.


9. Lastly, take your masses and divide each one by the volume. This will give you the density of each material.


So, there you go. Density is mass and volume. How heavy is it and how much space does it take up. If something has a great density, its atoms are very tightly packed together.


There’s a great story about Archimedes and density. The story goes that the king gave a crown maker a hunk of gold and the crown maker was supposed to make a crown using all the gold. Later the king got the crown but, being suspicious, wondered if the crown maker really used all the gold or if he cheated and kept some of it.


Supposedly the king was really bothered by this and felt he needed to find out. He went to Archimedes and asked him to find out if, indeed, he had been cheated or not. At the time, this was a very difficult question. Archimedes knew how heavy it should be if it was a certain volume, but only knew how to get the volume by multiplying length x width x height. How do you do that with an ornate crown? Needless to say the king was against smashing the crown into a cube!


The story goes that this problem possessed Archimedes and he spent so much time thinking about it that he rarely ate, rarely slept and never bathed! Supposedly, that behavior wasn’t that uncommon for him when he was tackling tough problems. Finally his servants, who could no longer stand it, dragged him kicking and screaming to the bath.


The story goes that Archimedes noticed, as he slipped into the bath, that the water rose around him. He discovered that the water he displaced was a way to measure his volume and lo and behold the same method could be used to measure the volume of the crown! Supposedly, he was so excited about this that he jumped out of the tub and ran through the streets stark naked yelling “Eureka! Eureka!” Which means “I found it! I found it!”. He used this method on the crown and to the king’s disappointment (and the crown maker’s too) the crown was indeed missing some gold.


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Quick & Easy Density

Friday October 2, 2009

Density is basically how tightly packed atoms are. (Mathematically, density is mass divided by volume.) For example, take a golf ball and a ping pong ball. Both are about the same size or, in other words, take up the same volume.


However, one is much heavier, has more mass, than the other. The golf ball has its atoms much more closely packed together than the ping pong ball and as such the golf ball is denser.


These are quick and easy demonstrations for density that use simple household materials:
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Density Jar

You will need to find:


  • glass jar
  • water
  • vegetable oil
  • liquid dish soap
  • honey
  • corn syrup
  • molasses
  • rubbing alcohol
  • lamp oil (optional)

Fill a clear glass partway with water. Drizzle in cooking oil. What do you see happening? Try adding in liquid dish soap (make sure it’s a different color form the water and the oil for better visibility.)


What else can you add in? What about honey, corn syrup, molasses, rubbing alcohol, or lamp oil? Use a turkey baster to help you pour the liquids in very slowly so they don’t mix. You’ll get the best results if you start with the heaviest liquids.



 
Download Student Worksheet & Exercises


Hot & Cold Swirl

To clearly illustrate how hot and cold air don’t mix, find two identical glasses.  Fill one glass to the brim with hot water.  Add a drop or two of red food coloring and watch the patterns.  Now fill the other glass to the top with very cold water and add drops of blue dye.  Do you notice a difference in how the food coloring flows?


Get a thick sheet of heavy paper (index cards work well) and use it to cap the blue glass.  Working quickly, invert the glass and stack it mouth-to-mouth with the red glass.  This is the tricky part: When the glasses are carefully lined up, remove the card.  Is it different if you invert the red glass over the blue?


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Play With Your Food

Friday October 2, 2009
This is a simple experiment that really shows the relationship of mass, volume, and density.  You don't need anything fancy, just a piece of bread.  If you do have a scale that can measure small masses (like a kitchen scale), bring it out, but it is not essential.

Here's what you do: [am4show have='p8;p9;p13;p40;' guest_error='Guest error message' user_error='User error message' ]

1. Grab a piece of bread.

2. If you have a scale, weigh the bread to get the mass of the bread.

3. Now, have a little fun and squish the bread into the smallest ball you can!

4. Check the weight (mass) again.

Soooo, what happened? The bread had the same mass before and after squishification right? But did it have the same density? Nope. You, very cleverly and with great strength squeezed those bread atoms closer together. So the bread ball, had a much higher density than the slice of bread did. Same mass, different volume.

Download Student Worksheet [/am4show]

Atomic Facts

Friday October 2, 2009

A gram of water (about a thimble of water) contains 1023 atoms. (That’s a ‘1’ with 23 zeros after it.) That means there are 1,000,000,000,000,000,000,000,000 atoms in a thimble of water! That’s more atoms than there are drops of water in all the lakes and rivers in the world.


Nearly all the mass of an atom is in its nucleus which occupies less than a trillionth of the volume of the atom. They are very dense. If you could pack nuclei like marbles, into something the size of a large pea, they would weigh about a billion tons! That’s 2,000,000,000,000 pounds! More than the weight of 20,000 battle ships! That’s a heavy pea!


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The distance from the nucleus to the electron is 100,000 times the diameter of the nucleus itself. So, if you were to somehow blow up a nucleus to be the size of a golf ball, the electron would be 8,300 feet away or more than 1.5 miles from the golf ball. If you put that golf ball on the ground, you would need to climb to the top of five and a half Sears Towers to get to the electron!


Danish physicist David Bohr, a famous scientist who won the Nobel Prize in Physics in 1922 for his work with the atomic structure.
Danish physicist David Bohr, a famous scientist who won the Nobel Prize in Physics in 1922 for his work with the atomic structure.

Let’s compare this to the Sun and the Earth. (In the picture on the left, the tiny dot in the left size is the actual size of the Earth. The Earth is really not this close to the sun – we just wanted you to get a feel for the sizes of both.) We’ll be doing more about distances and sizes when we do our lesson in Astronomy, but for now, we’ll just use this quick example:


If you shrank the Sun down to a golf ball, the Earth would only be 9 inches away. Nine inches vs. 1.5 miles! There is 11,000 times more distance (to scale) between the nucleus and an electron than there is between the Sun and the Earth!


Here’s one last example – if you enlarged the hydrogen atom (one proton in the nucleus and one electron in a shell) so that it’s the size of the Earth, the electron would be skimming along on the surface of the Earth while the nucleus (just a proton in this instance) would be only the size of a basketball deep inside the core. The rest, from the core to the surface, is empty space.  (Look out your window – can you even see the curvature of the Earth from where you are?  Probably not – it’s just too vast a distance!)


Are you mind-boggled? What this is basically saying, is that matter is virtually empty. The nucleus, which is incredibly tiny and quite heavy for it’s size, is outrageously far away from its electrons. An atom has almost nothing in it and yet everything we come in contact with is made of this ‘nothing’! I don’t know about you, but I find that fantastic!


We will talk more about this wacky atom thing and we’ll get into more detail about the even wackier electron. In the meantime, try to think about everything as a bunch of atoms. The next time you drink milk, you’re drinking atoms. The next time you feel wind, you’re feeling atoms. A lot of things become a bit clearer if you think of objects as being nothing more than bunches of small particles stuck together.


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Salt & Vinegar Crystals

Friday October 2, 2009

We’re going to take two everyday materials, salt and vinegar, and use them to grow crystals by creating a solution and allowing the liquids to evaporate.  These crystals can be dyed with food coloring, so you can grow yourself a rainbow of small crystals overnight.


The first thing you need to do is gather your materials.  You will need:


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Here’s what you need:


  • 1 cup of warm water
  • 1/4 cup salt (non-iodized works better)
  • 2 teaspoons to 2 tablespoons of vinegar (you decide how much you want to use)
  • a shallow dish (like a pie plate)
  • a porous material to grow your crystals on (like a sponge)

First, mix together the salt, vinegar, and water in a cup.  (You cal alternatively boil the water on the stove and stir in as much salt as the water will dissolve.)  Add the vinegar after you turn off the heat. Next, place your sponge in a bowl and pour the solution over the sponge, submerging the sponge in the solution.  Leave out, undisturbed, until the liquids evaporate, leaving behind a sheet of crystals.



 
Download worksheet and exercises


You can add more liquid carefully to the bowl to continue the growth of your crystals for long after the first solution dries up.  Also, as your crystals grow, dot the sponge with drops of food coloring to crow various colors of crystals.


Although it takes awhile for the crystals to start growing, once they do, they will continue to grow quickly!


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Eggshell Crystals

Friday October 2, 2009

Geodes are formed from gas bubbles in flowing lava. Up close, a geode is a crystallized mineral deposit that is usually very dull and ordinary-looking on the outside.  When you crack open a geode, however, it’s like being inside a crystal cave.  We’ll use an eggshell to simulate a gas bubble in flowing lava.


We’re going to dissolve alum in water and place the solution into an eggshell. In real life, minerals are dissolved in groundwater and placed in a gas bubble pocket.  In both cases, you will be left with a geode.


Note: These crystals are not for eating, just for looking.


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Here’s what you need:


  • clean egg shells
  • alum (check the spice section of the grocery store)
  • food dye
  • water


 
Download worksheet and exercises


This is a continuation of the Laundry Soap and Rock Candy experiments, so make sure you’ve done those before trying this one.


Find a clean half eggshell.  Fill a small cup with warm water and dissolve as much alum in the water as you can to make a saturated solution (meaning that if you add any more alum, it will fall to the bottom and not dissolve).


Fill the eggshells with the solution and set aside.  Observe as the solution evaporates over the next few days.  When the solution has completely evaporated, you will have a homemade geode.  If no crystals formed, then you had too much water and not enough alum in your solution.


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Salt Stalactites

Friday October 2, 2009

This is a continuation of the Laundry Soap and Rock Candy experiments, so make sure you’ve done those before trying this one.


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Here’s what you need:


two clean glass jars
yarn or string
epsom salts
water
tin foil or cook sheet
adult help, sauce pot, and a stove.


Make a supersaturated saturated solution from warm water and Epsom salts (magnesium sulfate).  (Add enough salt so that if you add more, it will not dissolve.)  Fill two empty glass jars with the salt solution.  Space the jars a foot apart on a layer of foil or on a cookie sheet.  Suspend a piece of yarn or string from one jar to the other.  Wait impatiently for about three days.  A stalactite should form from the middle of the string!



 
Download worksheet and exercises


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Lava Lamp

Friday October 2, 2009
We're going to watch how density works by making a simple lava lamp that doesn't need electricity! If you like to watch blob-type shapes shift and ooze around, then this is something you're going to want to experiment with.  but don't feel that you have to use the materials mentioned below - feel free to experiment with other liquids you have around the house, and be sure to let me know what you've found in the comment section below.

All you need is about 10 minutes and a few quick items you already have around the house.  Are you ready?

[am4show have='p8;p9;p13;p40;p68;p79;' guest_error='Guest error message' user_error='User error message' ] Here's what you need to find:
  • empty glass jar with straight sides (if possible)
  • vegetable oil
  • salt
  • water
  • food dye


Fill a water glass halfway with colored water, and add a 1/2" layer of oil on top. Shake salt over the oil layer and watch the lava lamp start to work! You'll see the bottom oil layer move as a salt-oil-drop falls to the bottom of the glass. Over a few minutes, the oil breaks free of the salt and moves back up to rejoin the oil layer on top.



Download Student Worksheet

What's happening? You're actually watching the salt itself fall through the oil. However, the oil sticks to the salt to form a larger object, and since the salt is heavier than oil and water, the whole mess plunks to the bottom of the glass. At the bottom of your cup, the oil breaks free of the salt (eventually) and rises back up. Does it matter if you heat the oil, chill the water, or vice versa? Is there anything that works better than salt?

Going Further: Unscrew the camp and add a broken-up effervescent tablet (like alka-seltzer) to your bottle. Cap it and watch what happens! Did it react with water, oil or both? What if you turn off the lights and shine a flashlight through it? [/am4show]

Water Glass & Metal Crystals

Friday October 2, 2009

This experiment is for advanced students. Water Glass is another name for Sodium Silicate (Na2SiO3), which is one of the chemicals used to grow underwater rock crystal gardens. Metal refers to the metal salt seed crystal you will use to start your crystals growing.  You can use any of the following metals listed.  Note however, that certain metals will give you different colors of crystals.


Your crystals begin growing the instant you toss in the seed crystals.  These crystals are especially delicate and fragile – just sloshing the liquid around is enough to break the crystal spikes, so place your solution in a safe location before adding your seed crystals.


After your garden has finished growing to the height and width you want, simply pour out the sodium silicate solution and replace with fresh water (or no water at all).  Due do the nature of these chemicals, keep out of reach of small children, and build your garden with adult supervision.


Here’s what you need to get:


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  • Clean glass jar
  • Sodium silicate (check shopping list for online ordering)
  • One (or more) of the following for different colors:
    • White – calcium chloride (found on the laundry aisle of some stores)
    • Purple – manganese (II) chloride
    • Blue – copper (II) sulfate (common chemistry lab chemical, also used for aquaria and as an algicide for pools)
    • Red – cobalt (II) chloride
    • Orange – iron (III) chloride


 
Download worksheet and exercises


The seed crystals are metal salts that react with the water/sodium silicate solution to climb upwards in the solution, as the products are less dense than the surrounding solution.


Troubleshooting: If you add too many seed crystals, your solution will turn cloudy and you’ll need to start all over again!  Add your seed crystals sparingly – you can always add more later.


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Charcoal Crystals

Friday October 2, 2009

Charcoal crystals uses evaporation to grow the crystals, which will continue to grow for weeks afterward.  You’ll need a piece of very porous material, such as a charcoal briquette, sponge, or similar object to absorb the solution and grow your crystals as the liquid evaporates.  These crystals are NOT for eating, so be sure to keep your growing garden away from young children and pets! This project is exclusively for advanced students, as it more involves toxic chemicals than just salt and sugar.


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The materials you will need for this project:


  • Charcoal Briquettes (or pieces of sponge or brick or porous rock)
  • Distilled Water
  • Uniodized Salt
  • Ammonia (Keep this out of reach of children!)
  • Laundry Bluing
  • Food Coloring (optional)
  • Pie Plate (glass or tin)
  • Measuring Spoons
  • Disposable Cup
  • Popsicle Stick


Download worksheet and exercises


The first thing you’ll need to whip up a batch of solution, then you’ll start growing your garden.  Here’s how you do it:


1. Into a disposable cup, stir together (use a popsicle stick to mix it up, not your good silverware) 1 cup of water, 1 tablespoon of ammonia, 1/2 cup of laundry bluing, and 1/2 cup of salt (non-iodized).


2. Place your charcoal or sponge in a pie tin and pour your solution from step 1 over it.


3. Wait impatiently for a few days to one week.  As the liquid evaporates, the salts are left behind, forming your crystals.


4. Continue to add more solution (to replace the evaporated solution) to keep your crystals growing.  Think of it as ‘watering’ (with your special solution) your crystals, which are growing in your ‘soil’ (sponge).


5. You can dot the sponge with drops of food coloring to grow different colors in your garden.


Questions to Consider…

Why do you think you needed ammonia and ‘laundry bluing’ for this experiment?  What is ‘laundry bluing’, anyway?  Why do the crystals form just on the porous object and not the glass/metal pie plate?   Let us know in the comment field below what you think:


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Unit 3: Matter (Density) Exercises

Friday October 2, 2009

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.
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Click here to download the K-8 Exercises & Answers in PDF format.


About Atoms:


1. What is the smallest stable building block of matter?


2. When you go swimming, what are you moving through?


3. What are three particles inside an atom?


4. What makes one atom different from another?


5. What is an element?


6. Where have almost all atoms come from?


7. What five elements are in all living things?


8. True or false: Matter is made of hard, tightly packed, little particles.


9. What do you call a bunch of atoms stuck together?


About Electrons:
1. How do electrons move?


2. Do electrons just go all over the place in an atom?


3. What is a shell?


4. How many shells can an atom have?


5. What determines how many shells an atom has?


6. How many electrons can be in the third shell of an atom?


7. How many shells does a Sodium atom have? Sodium has 11 electrons.


8. Why do atoms come together to form molecules?


About Density:
1. What is density?


2. Which is more dense, a one pound can of beans or a one pound loaf of bread?


3. Which is more dense a gallon of water that weighs 8 lbs or a gallon of gasoline that weighs 6 lbs?


4. Which is more dense, a school bus filled with children or an empty school bus?


For Advanced Students:

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Click here to download the K-12 Exercises & Answers in PDF format.


As always, if math isn’t your thing, feel free to skip this. Density = mass divided by volume or d=m/v.


1. What is the density of an egg that has a mass of 51 g and has a volume of 50 ml?


2. What is the density of an apple that has a mass of 170 g and has a volume of 160 ml?


3. Can you use the technique used in Experiment 2 to find the density of a “D” cell battery? Follow steps 6 through 9 but put the battery directly into the container without putting it into the cup. This will give you the volume of the battery . When you’re done check out my answer below.


4. Which is more dense ketchup or water? Use these measurements for your calculations. Ketchup: 650ml and 680 g Water: 500 ml and 500 g


5. Of the water, apple, battery and egg, which one had the greatest density? Which one had the least?


Need answers?
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Unit 3: Matter (Solids) Exercises

Friday October 2, 2009

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.
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Click here to download the K-8 Exercises & Answers in PDF format.


1. What is the lowest energy form of matter found naturally?


2. What is the highest energy form of matter?


3. Why do many solids form crystals?


4. If I bend a pencil so far that it breaks, what have I done to it?


5. I love to play with paper clips. However, by the time I’m done with them they are all bent out of shape. (Paper clips run when they see me coming!) How can you explain that using a term from this lesson.


6. Why do crystals tend to break along specific lines?


Need answers?


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Unit 3: Matter (Density) Answers to Exercises

Friday October 2, 2009

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Answers:
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About Atoms:
1. The atom.


2. Billions and billions of atoms.


3. Neutron, proton (in the nucleus) and electron.


4. The number of particles inside the atom. Atoms are made of identical stuff. It’s the number of particles (neutrons, protons, and electrons) that make atoms have different characteristics.


5. Elements are specific kinds of atoms. Each element (each specific atom) has a different behavior from every other element.


6. Exploded stars.


7. Carbon, Hydrogen, Oxygen, Nitrogen, Calcium: CHONC


8. False. Matter is made of atoms that have incredible distances between their incredibly tiny bits of matter.


9. A molecule.


About Electrons:
1. They pop in and out of existence.


2. No. They tend to stay a certain distance away from the nucleus.


3. A shell is the distance that electrons tend to stay in as they pop around the nucleus.


4. Up to seven.


5. The number of electrons an atom has.


6. 18. Remember 2n2. So 2 x 32 = 18.


7. 2 atoms fill the first shell, 8 fill the second, and 1 is left in the third. So Sodium has 3 shells.


8. Because they are “unsatisfied’. They have too many or not enough electrons in their outer shell.


About Density:
1. Density is a measurement of how heavy something is and how much space it takes up. In other words, a measurement of its mass and its volume.


2. The beans are more dense since they have less volume (the can of beans is smaller then the loaf of bread).


3. Believe it or not, gasoline is less dense than water.


4. A full school bus. Both have the same volume but the full one will have more mass.


For Advanced Students:

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1. Egg 51g/50ml = 1.02 g/ml


2. Apple 165g/170ml = .97 g/ml


3. I got about 40 ml for the battery’s volume and 140 g for its mass. With those figures the density is : 140g/40ml= 3.5 g/ml


4. Ketchup is more dense.


Ketchup 680 g/ 650 ml= 1.05 g/ml


Water 500g/ 500 ml= 1 g/ml


5. The battery had the greatest density at 3.5 g/ml. The object with the least density was the apple at .97 g/ml. By the way, the objects with a lower density than water sank. The objects with a higher density than water floated. Coincidence? Nope, we’ll look into that more when we get to the buoyancy lesson.


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Unit 3: Matter (Solids) Answers to Exercises

Friday October 2, 2009

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Answers:
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1. Solids. Remember BEC is only found in science labs.


2. Plasma.


3. The molecules are pulled so tightly together that they tend to fall into specific patterns.


4. I have bent it beyond its tension and/or compression point.


5. I have bent the paper clip beyond its point of elasticity so it no longer snaps back to its original shape.


6. Crystals break along cleavage lines which are there due to the way the molecules lined up when the crystal formed.


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