ChemShorts for Kids   --   1995
Copyright ^©1995 by the Chicago Section of the American Chemical Society

Into a bowl add 1 cup heavy whipping cream, 1 cup half & half, 1/3 cup sugar, 1 egg, and 1 teaspoon vanilla extract. After whisking for a few minutes, pour half of the mixture into a sandwich-size ziploc baggie and seal. Into a gallon-size ziploc baggie add four good handfuls of rock salt and eight good handfuls of crushed ice. Seal this baggie and gently shake the ice-salt mixture around until a good amount of water is formed. Rock salt is a chunkier version of common table salt (sodium chloride), but it is not clean enough to eat. Place the sandwich baggie into the gallon-size baggie and seal. Mix it around so that the smaller baggie is in contact with the cold water as much as possible. The material in the little bag should thicken in 10-15 minutes. When it is thick enough, take the small baggie out of the large one and scoop the contents into a cup for your very own edible treat.

The milk solution becomes thicker because it is freezing. When a liquid freezes it turns into a solid form. The salt-ice mixture should feel very cold, and though it will be hard to feel a difference, it is colder than the ice by itself. The experiment would take much longer if you used ice alone. The ice would melt quickly and need to be replaced often. So, how do you make the ice colder? The trick is adding the salt. It is a well-known phenomenon to chemists that a solution, such as salt-water, will freeze at a lower temperature than a pure liquid, such as water. So your salt-ice water solution is colder than just ice water alone. The same principle is being used when salt is sprinkled on icy roads in the wintertime.

Use blunt end scissors to cut 3 strips from a cone-type coffee filter that are about 10 cm long and 3 cm wide. Using a pencil, write at the end of each strip the name of one candy. Pour about 1/4 cup of water into a clear plastic cup. Wet one end of a cotton swab and gently wet one side of a candy. Gently rub the candy's wet candy coating onto its filter strip. Make the dark dot on the paper about 2 cm from the unwritten end, in the center. Do not use the dirty end of the cotton swab again. Repeat this procedure for the other two candies, using a clean cotton swab each time. When they are dry, carefully place the strips in the cup of water so that only the very end of each strip touches the water. The end with the writing can be folded over the rim of the cup to keep the strip in place. Be sure the colored dots are above the surface of the water, otherwise all the coloring will simply wash out in the solution.

Cover a work area with paper towels. Label 3 clear 8 oz plastic cups as "water", "water and plaster", and "soapy water". Pour 1/2 cup warm water into each cup. Add about 1/4 teaspoon of plaster of paris powder to the cup labeled "water and plaster". Stir thoroughly with a plastic straw. Grate 1-2 tablespoons of soap from a bar of soap. Put about 1 tablespoon into the "soapy water" labeled cup. Stir thoroughly with a new straw. Add 1 tablespoon of your soapy water to the "water" and "water and plaster" cups. Do not stir right away, and observe what happens closely. Is there a difference? What do you see happening in one of the cups? Now stir each cup with a separate straw. Do they still look different? Next use a new clean straw to blow gently into each cup. Do you notice a difference in the bubbling? What do you think is the reason? It will help you to know that plaster of paris is a chemical compound called calcium sulfate (made from gypsum).

Pop exactly 1/4 cup of fresh popcorn in a hot air popcorn popper, and then do the same with the dried kernels. Measure the volume of each of your results. Some kitchens have large glass measuring cups than can be used for this, or else just use similar sized bowls or drinking cups and "eyeball it".

The fresh popcorn should produce a larger volume of popped corn. Popcorn is mostly starch and water. As the kernel is heated, the water inside turns to steam. So much steam pressure can build up inside the kernel that the outer layer finally cannot hold it back and the kernel explodes. The starch expands into the familiar white substance that we have all come to know as popcorn. So now can you guess why the dried kernels resulted in a lower volume? Most of their moisture was evaporated beforehand, slowly and intentionally, so that there was not enough left to explode the kernel as much.

You will need a can of Scotchguard® spray, facial tissue, 2 clear plastic cups, 2 rubber bands, and water. You will also need proper ventilation because of the Scotchguard® spray fumes.

Open one tissue and drape over one of the cups. Push the center of the tissue slightly into the cup, forming a pocket. Secure it to the cup with a rubber band. Slowly pour some water into this pocket and observe what happens. Now spray a new tissue with Scotchguard®, let it dry, and repeat the experiment. What happens? Does this tissue cause different behavior?

The old-fashioned white kind of peanuts are made of Styrofoam, which is an expanded version of a polymer called polystyrene. The newer kind is called Ecofoam and it is made from corn starch. The most obvious difference between them in terms of chemical properties is that Ecofoam will dissolve in water while Styrofoam will not. Just put a foam peanut in a cup of water and wait a few minutes. The warmer the water the faster the Ecofoam will dissolve. Can you think of a way to take advantage of this difference for a useful purpose? Of course the answer is fairly obvious. Ecofoam was deliberately made as an alternative to Styrofoam because it will quickly degrade in the environment. It is therefore a more ecologically- and environmentally-friendly packaging peanut. (Can you see that Ecofoam would not make a very good beverage container, however?)

If you have an adult partner that has access to acetone (the active ingredient in many nail polish removers), they can show you that Styrofoam will "melt" in acetone while Ecofoam will not. This could therefore be one way to reduce the space that Styrofoam products take up as waste.

With your adult partner, turn on a hose and make a fine spray using a nozzle or your thumb. Move so that you are looking at the water with the sun behind you. Spray harder or softer and higher or lower until you see a rainbow. Try changing your position so that the sun hits your water from a different angle. Or try having your partner spray the water while you view from different angles and distances. If you are successful, note the order of the colors.

Light is an electromagnetic wave of energy. Some electromagnetic waves have higher energies than others. The whole range is called the electromagnetic spectrum. Waves in this spectrum include X-rays, microwaves, radio waves, visible light, and others. The waves of visible light, which is what we can see, are in the middle of this spectrum. Their energies are lower than those of X-rays, but higher than those of microwaves and radio waves. The colors appear in order according to their energy. From the lowest energy to the highest energy the colors appear as

red, orange, yellow, green, blue, indigo, and violet.