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Lesson #32: Acids and Bases

Lesson #33: Making Litmus Paper

You can go your whole life without paying any attention to the chemistry behind acids and bases. But you use acids and bases all the time! They are all around you. We identify acids and bases by measuring their pH.

Every liquid has a pH. If you pay particular attention to this lab, you will even be able to identify most acids and bases and understand why they do what they do. Acids range from very strong to very weak. The strongest acids will dissolve steel. The weakest acids are in your drink box. The strongest bases behave similarly. They can burn your skin or you can wash your hands with them.

Acid rain is one aspect of low pH that you can see every day if you look for it. This is a strange name, isn’t it? We get rained on all the time. If people were dissolving, if the rain made their skin smoke and burn, you’d think it would make headlines, wouldn’t you? The truth is acid rain is too weak to harm us except in very rare and localized conditions. But it’s hard on limestone buildings.

Acids are liquids with a pH less than seven. A pH of seven is considered neutral. Bases are liquids with a pH greater than seven.

The combustion of fossil fuels such as oil, gasoline, and coal, create acid rain. Rain, normally at a pH of about 5.6, is always at least slightly acidic. Carbon dioxide is released into the air reacts with moisture in the air to form carbonic acid (HCO₃). Sulfur dioxide and nitrogen oxides are released into the air by fossil fuel combustion. They react with the slightly acidic rain and form sulfuric acid (H₂SO₄) and nitric acid (HNO₃).

We’re going to have fun with color changes in this experiment. We will make magic paper that changes color to tell us important things about liquids. It’s called litmus paper.

Litmus is harvested from a plant called a lichen, and bottled up as a powder. We’ll take the powder and make an acid-base indicator with it. Then we will use what we make to test solutions. And if you exercise your mind a bit, you will discover ways to use your litmus paper to discover things about the house and the world around you.

Materials:

Test tube rack
2 Test tubes
Test tube stopper
Distilled water
Ruler
Litmus powder (MSDS)
Measuring spoon
Denatured alcohol (MSDS)
Pipette
Sodium carbonate (Na₂CO₃) (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.
Scissors
Filter paper (or paper towel or coffee filter)
Impervious surface

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.

We will be using a ruler to measure the amount of water in a test tube. Ordinarily, chemists use more accurate measurement tools than a ruler. For the first part of this lab, making litmus solution, all we need is an approximate volume of water.

We will also be shaking a liquid in a test tube. Ever leave the top of a blender off when the “on” button is depressed? If not, just believe that it’s not a good idea. There is a certain technique t use when shaking up a liquid. We’ll place a stopper on a test tube and shake vigorously. Remember to do that as a chemist would do.

In a laboratory, whenever a chemist stoppers a solution and shakes it, it will be done the same way no matter if it is a toxic substance or just salt and water. That way, they are in the habit of doing it one way, the right way, so a mistake is not made at any time. A mistake at the wrong time could even be fatal.

Stopper the test tube firmly. Seat it well, but don’t grind down on the stopper. A test tube is thin-walled glassware, and as we grip harder it could collapse in our hand and now we have open cuts, blood, and toxic chemical is now entering your bloodstream. Stoppered firmly, we hold the test tube in our hand and place our thumb over the stopper for added security. To top off our safety measures, point the test tube, with a thumb firmly on top, away from us or anyone else and shake to our heart’s content.

We need to be careful with our chemicals. After using a chemical, cap the container to prevent spillage and contamination. Clean everything thoroughly after you are finished with the lab, or if you are going to reuse a tool. To dip a measuring spoon into one chemical after another, contaminates the chemicals and will affect your results.

Download Student Worksheet & Exercises

Clean everything thoroughly after you are finished with 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.

Place all chemicals, cleaned tools, and glassware in their respective storage places.

Dispose of all solid waste in the garbage. Liquids can be washed down the drain with running water. Let the water run awhile to ensure that they have been diluted and sent downstream.

You can test how acidic different substances are with an acid-base indicator like litmus paper.

Using the litmus powder in the chemistry set, we will make litmus paper. Our litmus paper is going to start out blue, and will turn red when an acid is placed on it. You can turn it back to blue by placing a few drops of a basic solution on it.

Let’s look a little further into the chemistry behind acids and bases. An acid produces hydronium ions (example: H₃O⁺) when dissolved in water. The ⁺ or ^– notation on a molecule tells us that after a chemical reaction creates it, the molecule is left with a net positive (electrons have been lost) or net negative charge (electrons have been added). Now, the ion could have more than just a +1 or -1 charge. Often, we will discover molecules with positive or negative charges of 2, 3, or 4.

Every liquid has a pH, and some of them may surprise you. Fruits contain citric acid, malic acid, and ascorbic acids, and the distilled white vinegar in your kitchen is a weak form of acetic acid. You’ll find carbonic acids in sodas, and lactic acid in buttermilk. And remember that acids taste sour and bases taste bitter? Don’t taste your chemicals, but the sour taste of vinegar and lemons and the bitter taste of club soda water and baking soda are familiar to people.

Generally, acids are sour in taste, change litmus paper from blue to red, react with metals to produce a metal salt and hydrogen, react with bases to produce a salt and water, and conduct electricity. Strong acids often produce a stinging feeling on mucus membranes (don’t ever taste an acid, or any chemical for that matter!).

Acids are proton donors (they produce H⁺ ions). Strong acids and bases all have one thing in common: they break apart (completely dissociate) into ions when placed in water. This means that once you dunk the acid molecule in water, it splits apart and does not exist as a whole molecule in water. Strong acids form H⁺ and an anion, such as sulfuric acid:

H₂SO₄ –> H⁺+ HSO₄

There are six strong acids:

hydrochloric acid (HCl)
nitric acid (HNO₃) used in fireworks and explosives
sulfuric acid (H₂SO₄) which is the acid in your car battery
hydrobromic acid (HBr)
hydroiodic acid (HI)
perchloric acid (HClO₄)

The record-holder for the world’s strongest acid are the carborane superacids (over a million times stronger than concentrated sulfuric acid). Carborane acids are not highly corrosive even though are super-strong. Here’s the difference between acid strength and corrosiveness: the carborane acid is quick to donate protons, making it a super-strong acid. However, it not as reactive (negatively charged) as hydrofluoric (HF) acid, which is so corrosive that it will dissolve glass, many metals, and most plastics.

What makes the HF so corrosive is the highly reactive Fl^– ion. Even though HF is super-corrosive, it’s not a strong acid because it does not completely dissociate (break apart into H⁺ and Fl^–) in water. Do you see the difference? Weak acids only partly dissociate in water, such as acetic acid (CH₃COOH).

On the other hand, bases taste bitter (again, don’t even think about putting these in your mouth!), feel slippery (don’t touch bases with your bare hands!), don’t change the color of litmus paper, but can turn red litmus back to blue, conduct electricity when in a solution, and react with acids to form salts and water. Soaps and detergents are usually bases, along with house cleaning products like ammonia.

Bases are also electron pair donors (they produce OH^– ions). Strong bases also completely dissociate into the OH^– (hydroxide ion) and a cation. LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH (potassium hydroxide), RbOH (rubidium hydroxide), CsOH (cesium hydroxide), Ca(OH)₂ (calcium hydroxide), Sr(OH)₂ (strontium hydroxide), and Ba(OH)₂ (barium hydroxide). Weak bases only partly dissociate in water, such as ammonia (NH₃)

pH stands for “power of hydrogen” and is a measure of how acidic a substance is. We can make homemade indicators to test how acidic (or basic) something is by squeezing out a special kind of juice (dye) called anthocyanin. Certain flowers have anthocyanin in their petals, which can change color depending on how acidic the soil is (hibiscus, hydrangeas, and marigolds for example). The more acidic a substance, the more red the indicator will become.

Going Further

Experiment: What household items are acidic or basic? Test various liquids to see. You may be surprised. Liquids you should be sure to test are vinegar, lemon or orange juice, baking soda, and cola. Use a dropper to place drops onto the paper instead of dunking the strip into your entire carton of orange juice. Litmus flavored orange juice is not my first choice in the morning.

Experiment: Collect soil samples from various places. Not the types of plants growing in the immediate area you are sampling from. Place about an inch of dirt in the bottom of a test tube. Fill the test tube near the top with water. Use distilled water if you have it for more accuracy. Stopper the tube and shake vigorously. Use your pipette to place drops of the water on your litmus paper and see if the soil is acidic or basic. Is there a correlation between the acidity of the soil and the plants that grow there?

Note: Litmus paper will not be able to indicate how acidic the rain in your area is, because the acid content in the water droplet is not high enough to register on the indicator. The effects of acid rain take time to develop and require more sensitive equipment to detect.

Lesson #34: Bicarbonate Buffer

All chemical reactions are equilibrium reactions. This experiment is really cool because you’re going to watch how a chemical reaction resists a pH change.

Materials:

baking soda
universal indicator
distilled white vinegar
3 test tubes with stoppers
distilled water
medicine droppers
clear soda
safety goggles and gloves

First add water to a test tube and then add 10 drops of universal indicator and shake it up.
Compare the color with your color chart and find the pH number. Set aside.
Into a second test tube, add baking soda and water. Shake it up again!
Add 10 drops universal indicator and shake the second test tube up again.
Compare the second test tube with the pH chart to find the number.
Using your medicine dropper, place soda to the second test be and look for a color change.
Keep adding dropper-fulls of soda until you get the pH to match the first test tube (7).
Add two drops of distilled white vinegar and look for a color change. Add more drops as needed.
What happened?

We had two solutions that were both around 7. When we added an acid to one of them, the pH should have decreased. But why when we added the acid to the baking soda-carbonated soda solution, did it not change at all? That’s because it’s a buffer solution, which resists changes in pH.

Lesson #35: Acids and Bases

If you had a choice between a glass of lemon juice or apple juice, most folks would pick the sweeter one – apple. Did you know that apples are loaded with malic acid, and are actually considered to be acidic? It’s just that there is so much more sugar in an apple than a lemon that your taste buds can be fooled. Here’s a scientific way (which is much more reliable) to tell how acidic something is.

Acids are sour tasting (like a lemon), bases are bitter (like unsweetened cocoa powder). Substances in the middle are more neutral, like water. Scientists use the pH (power of hydrogen, or potential hydrogen) scale to measure how acidic or basic something is. Hydrochloric acid registers at a 1, sodium hydroxide (drain cleaner) is a 14. Water is about a 7. pH levels tell you how acidic or alkaline (basic) something is, like dirt. If your soil is too acidic, your plants won’t attract enough hydrogen, and too alkaline attracts too many hydrogen ions. The right balance is usually somewhere in the middle (called ‘pH neutral’). Some plants change color depending on the level of acidity in the soil – hydrangeas turn pink in acidic soil and blue in alkaline soil.

There are many different kinds of acids: citric acid (in a lemon), tartaric acid (in white wine), malic acid (in apples), acetic acid (in vinegar), and phosphoric acid (in cola drinks). The battery acid in your car is a particularly nasty acid called sulfuric acid that will eat through your skin and bones. Hydrochloric acid is found in your stomach to help digest food, and nitric acid is used to make dyes in fabrics as well as fertilizer compounds.

Materials:

Litmus paper or pH paper (you can cut into strips)
apple
lemon
vinegar
baking soda
cup with water

Here’s a video that shows you how to test several different things, including how to safely test stronger acids and bases, should you wish to test your own out.

Some things you can test (in addition to the ones in the video) include: Sprite, distilled white vinegar, baking soda, Vanish, laundry detergent, clear ammonia, powdered Draino, and Milk of Magnesia. DO NOT mix any of these together! Simply add a bit to each cup and test it with your pH strips. Here’s a quick video demonstration:

(Note – we didn’t list the chemicals on the shopping list as there were a LOT of stuff to get for only one experiment, so just sit back and watch!)

No pH strips? The chop up a head of red cabbage and whirl in a blender with water. Pass through a strainer (discard the solids), and pour this new ‘indicator’ into several cups. Add Sprite to one cup and watch for a color change. Add baking soda and watch for another color change. Continue down the line, adding only one chemical per cup into your cabbage juice.

Lesson #36: Water to Wine

Phenolphthalein is a weak, colorless acid that changes color when it touches acidic (turns orange) or basic (turns pink/fuchsia) substances. People used to take it as a laxative (not recommended today, as ingesting high amounts may cause cancer). Use gloves when handling this chemical, as your skin can absorb it on contact. I’ll show you how:

Materials:

2 test tubes
sodium carbonate (washing soda)
phenolphthalien (liquid)
medicine dropper
water
test tube stoppers
gloves and goggles

Download Student Worksheet & Exercises

Sprinkle a tiny amount of sodium carbonate into the bottom of your test tube. Fill your test tube partway with water (the solution should still be clear). Add a few drops of phenolphthalein (which is clear inside the dropper), cap, and shake.

Lesson #37: Gas-Forming Reactions

Lesson #38: Rubber eggs

If you soak chicken bones in acetic acid (distilled vinegar), you’ll get rubbery bones that are soft and pliable as the vinegar reacts with the calcium in the bones. This happens with older folks when they lose more calcium than they can replace in their bones, and the bones become brittle and easier to break. Scientists have discovered calcium is replaced more quickly in bodies that exercise and eating calcium rich foods, like green vegetables.

This is actually two experiments in one – here’s what you need to do:

Materials:

hard boiled egg
glass or clean jar
distilled white vinegar

Download Student Worksheet & Exercises

When you first plop the egg in the vinegar, do you notice the tiny bubbles? The acetic acid (distilled vinegar) reacts with the calcium carbonate in the eggshell, and you may even notice a color change over a couple of days.

How high does your egg bounce? Does it matter how long you leave it in the vinegar for?

The second part of this experiment is to try this again, but now use a raw egg (wash your hands after handling your egg due to salmonella!) You’ll get a difference result – the eggshell will become flexible, but don’t bounce them.

Exercises

Describe what the eggshell looked like before the reaction.
Describe the acetic acid
The product you witnessed in this chemical reaction was carbon dioxide, a colorless, odorless gas. How can you tell there really was a chemical reaction?
Why did the egg turn to “rubber?”

Lesson #39: POP Rockets

Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit nozzles.

According to the universal laws of motion, for every action, there is equal and opposite reaction. If flames shoot out of the rocket downwards, the rocket itself will soar upwards. It’s the same thing if you blow up a balloon and let it go—the air inside the balloon goes to the left, and the balloon zips off to the right (at least, initially, until the balloon neck turns into a thrust-vectored nozzle, but don’t be concerned about that just now).

A rocket has a few parts different from an airplane. One of the main differences is the absence of wings. Rockets utilize fins, which help steer the rocket, while airplanes use wings to generate lift. Rocket fins are more like the rudder of an airplane than the wings.

Another difference is the how rockets get their speed. Airplanes generate thrust from a rotating blade, whereas rockets get their movement by squeezing down a high-energy gaseous flow and squeezing it out a tiny exit hole.

If you’ve ever used a garden hose, you already know how to make the water stream out faster by placing your thumb over the end of the hose. You’re decreasing the amount of area the water has to exit the hose, but there’s still the same amount of water flowing out, so the water compensates by increasing its velocity. This is the secret to converging rocket nozzles—squeeze the flow down and out a small exit hole to increase velocity.

There comes a point, however, when you can’t get any more speed out of the gas, no matter how much you squeeze it down. This is called “choking” the flow. When you get to this point, the gas is traveling at the speed of sound (around 700 mph, or Mach 1). Scientists found that if they gradually un-squeeze the flow in this choked state, the flow speed actually continues to increase. This is how we get rockets to move at supersonic speeds or above Mach 1.

You can think of a shock wave as big pressure front. In this photo, the pressure is condensing water vapor in the air, hence the cloud. There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound.

The rockets we’re about to build get their thrust by generating enough pressure and releasing that pressure very quickly. You will generate pressure both by pumping and by chemical reaction, which generates gaseous products. Let’s get started!

For this experiment, you will need:

film canister or other plastic container with a tight-fitting lid (like a mini-M&M container)
alka-seltzer or generic effervescent tablets
water
outside area for launching

The record for these rockets is 28′ high. What do you think about that? Note – you can use anything that uses a chemical reaction… what about baking soda and vinegar? Baking powder? Lemon juice?

Important question: Does more water, tablets, or air space give you a higher flight?

Variations: Add foam fins and a foam nose (try a hobby or craft shop), hot glued into place. Foam doesn’t mind getting wet, but paper does. Put the fins on at an angle and watch the seltzer rocket spin as it flies skyward. You can also tip the rocket on its side and add wheels for a rocket car, stack rockets, for a multi-staging project, or strap three rockets together with tape and launch them at the same time! You can also try different containers using corks instead of lids.

More Variations: What other chemicals do you have around that also produces a gas during the chemical reaction? Chalk and vinegar, baking soda, baking powder, hydrogen peroxide, isopropyl alcohol, lemon juice, orange juice, and so on.

Lesson #40: Preparing Solutions

Lesson #41: Matrix

If you love the idea of mixing up chemicals and dream of having your own mad science lab one day, this one is for you. You are going to mix up each solid with each liquid in a chemical matrix.

In a university class, one of the first things you learn in chemistry is the difference between physical and chemical changes. An example of a physical change happens when you change the shape of an object, like wadding up a piece of paper. If you light the paper wad on fire, you now have a chemical change. You are rearranging the atoms that used to be the molecules that made up the paper into other molecules, such as carbon monoxide, carbon dioxide, ash, and so forth.

How can you tell if you have a chemical change? If something changes color, gives off light (such as the light sticks used around Halloween), or absorbs heat (gets cold) or produces heat (gets warm), it’s a chemical change.

What about physical changes? Some examples of physical changes include tearing cloth, rolling dough, stretching rubber bands, eating a banana, or blowing bubbles.

About this experiment: Your solutions will turn red, orange, yellow, green, blue, purple, hot, cold, bubbling, foaming, rock hard, oozy, and slimy, and they’ll crystallize and gel — depending on what you put in and how much!

This is the one set of chemicals that you can mix together without worrying about any lethal gases. I do recommend doing this OUTSIDE, as the alcohol and peroxide vapors can irritate you. Always have goggles on and gloves on your hands, and a hose handy in case of spills. Although these chemicals are not harmful to your skin, they can cause your skin to dry out and itch. Wear gloves (latex or similar) and eye protection (safety goggles), and if you’re not sure about an experiment or chemical, just don’t do it. (Skip the peroxide and cold pack if you have small kids.)

Materials:
• sodium tetraborate (borax, laundry aisle)
• sodium bicarbonate (baking soda, baking aisle)
• sodium carbonate (washing soda, laundry aisle)
• calcium chloride (AKA “DriEz” or “Ice Melt”)
• citric acid (spice section, used for preserving and pickling)
• ammonium nitrate (single-use disposable cold pack)
• isopropyl rubbing alcohol
• hydrogen peroxide
• acetic acid (distilled white vinegar)
• water
• liquid dish soap (add to water)
• muffin tin or disposable cups
• popsicle sticks for stirring and mixing
• tablecloths (one for the table, another for the floor)
• head of red cabbage (indicator)

Download Student Worksheet & Exercises

Step 1: Cover your kitchen table with a plastic tablecloth (and possibly the floor). Place your chemicals on the table. A set of muffin cups make for an excellent chemistry experiment lab. (Alternatively, you can use empty plastic ice cube trays.) You will mix in these cups. Leave enough space in the cups for your chemicals to mix and bubble up — don’t fill them all the way when you do your experiments!

Step 2: Set out your liquid chemicals in easy-to-pour containers, such as water bottles (be sure to label them, as they all will look the same): alcohol, hydrogen peroxide, water, acetic acid, and dish soap (mixed with water). Set out small bowls (or zipper bags if you’re doing this with a crowd) of the powders with the tops of your water bottles as scoopers. The small scoopers regulate the amounts you need for a muffin-sized reaction. Label the powders, as they all look the same.

Step 3: Prepare the indicator by coarsely chopping the head of red cabbage and boiling the pieces for five minutes in a pot full of water. Carefully strain out all the pieces with a fine-mesh strainer; the reserved liquid is your indicator (it should be blue or purple).

When you add this indicator to different substances, you will see a color range: hot pink, tangerine orange, sunshine yellow, emerald green, ocean blue, velvet purple, and everything in between. Test out the indicator by adding drops of cabbage juice to something acidic, such as lemon juice, and see how different the color is when you add indicator to a base, such as baking soda mixed with water.

Have your indicator in a bottle by itself. An old soy sauce bottle with a built-in regulator that keeps the pouring to a drip is perfect. You can also use a bowl with a bulb syringe, but cross-contamination could be a problem. Or it could not be — depending on whether you want the kids to see the effects of cross-contamination during their experiments. (The indicator bowl will continually turn different colors throughout the experiment.)

Step 4: Start mixing it up! When I teach this class, I let them have at all the chemicals at once (even the indicator), and of course, this leads to a chaotic mix of everything. When the chaos settles down, and they start asking good questions, I reveal a second batch of chemicals they can use. (I have two identical sets of chemicals, knowing that the first set will get used up very quickly.)

Step 5: After the initial burst of enthusiasm, your kids will instinctively start asking better questions. They will want to know why their green goo is creeping onto the floor while someone else’s just bubbled up hot pink, seemingly mixed from the same stuff. Give them a chance to figure out a more systematic approach, and ask if they need help before you jump in to assist.

What’s happening with the indicator? An indicator is a compound that changes color when you dip it in different things, such as vinegar, alcohol, milk, or baking soda mixed with water. There are several extracts you can use from different substances. You’ll find that different indicators are affected differently by acids and bases. Some change color only with an acid, or only with a base. Turmeric, for example, is good only for bases. (You can prepare a turmeric indicator by mixing 1 teaspoon turmeric with 1 cup rubbing alcohol.)

Why does red cabbage work? Red cabbage juice has anthocyanin, which makes it an excellent indicator for these experiments. Anthocyanin is what gives leaves, stems, fruits, and flowers their colors. (Did you know that certain flowers, such as hydrangeas, are blue in acidic soil but turn pink when transplanted to a basic soil?) You’ll need to get the anthocyanin out of the cabbage and into a more useful form so you can use it as a liquid indicator.

Tip for Testing Chemical Reactions: Periodically hold your hand under the muffin cups to test the temperature. If it feels hot, it’s an exothermic reaction (giving off energy in the form of heat, light, explosions …). The chemical-bond energy is converted to thermal energy (heat) in these experiments. If it feels cold, you’ve made an endothermic reaction (absorbing energy, where the heat from the mixture converts to bond energy). Sometimes you’ll find that your mixture is so cold that it condenses the water outside the container (like water drops on the outside of an ice-cold glass of water on a hot day).

Variations for the Indicator: Red cabbage isn’t the only game in town. You can make an indicator out of many other substances, too. Here’s how to prepare different indicators:
• Cut the substance into smaller pieces. Boil the chopped substance for five minutes. Strain out the pieces and reserve the juice. Cap the juice (indicator) in a water bottle, and you’re ready to go.
• What different substances can you use? We’ve had the best luck with red cabbage, blueberries, red and green grapes, beets, cherries, and turmeric. You can make indicator paper strips using paper towels or coffee filters. Just soak the paper in the indicator, remove and let dry. When you’re ready to use one, dip it in partway so you can see the color change and compare it to the color it started out with.
• Use the indicator both before and after you mix up chemicals. You will be surprised and dazzled by the results!

Teaching Tips: You can make this lab more advanced by adding a postage scale (to measure the solids in exact measurements), small beakers and pipettes for the liquid measurements, and data sheets to record temperature, reactivity, and acid/base indicator levels. (Hint: Make the data sheet like a matrix, to be sure you get all the possible combinations.)

For the student: Your mission is to mix up solutions that:
• Generate heat (exothermic)
• Get ice-cold on their own (endothermic)
• Crystallize
• Are self-gelling
• Bubble up and spit
• Ooze creepy concoctions
• Are the most impressive (the ooohhhh-aaahhhhh factor).

For the parent: Your mission is to:
• Make sure everything in reach is covered with plastic tablecloths, drop cloths, or tarps
• Open all the windows and turn on the fans (or just do this experiment outside near the hose)
• Keep all small children and pets away
• Slap on a pair of rubber gloves
• Encourage the kids to try it and test it
• Remember that there are no such things as mistakes, only learning opportunities. (Don’t forget that we usually learn more from mistakes than we do when we’re successful!)

For the truly exceptional parent: Your mission is also to:
• Secretly get an identical second set of chemicals from the grocery store (see shopping list above) and hide them in a bin nearby
• Have all the chemicals out and ready for the kids to use
• Be sure the kids know your rules before you let them loose (no eating, running, or horseplay; all goggles must stay on; etc.)
• Have a bin full of water nearby for washing up
• Let the kids loose to experiment and play without expectation
• Play with the kids, get into the act (“Wow! It turned green! How did you do that?!” instead of “Well, I’m not going to clean THAT up.”)
• Expect kids to dump everything and mix it all together at the same time without much thought about what they are trying to accomplish
• When their supplies run out, pull out your second bin and smile
• Encourage the kids to try their ideas out
o When they ask, “Will this work?” you can reply
with confidence, “I don’t know — try it!”

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