ChemShorts for Kids   --   1996
Copyright ^©1996 by the Chicago Section of the American Chemical Society

Bubble gum is a mixture of several chemicals, but rubber is the most important. A good bubble gum must be strong enough to stretch to a thin film without breaking, but still be soft enough to chew easily. That's a tall order. The other chemicals in bubble gum - resins, waxes, fillers, flavors, sugar, humectants, and emulsifiers - are all there either to provide flavor or to modify when and by how much the rubber stretches. Rubber molecules are polymers, which are long chain-like molecules formed when many smaller molecules bond together end to end. A natural polymer called latex, which is from trees, used to provide the stretchy part of bubble gum. Now many gum companies use a synthetic, food-grade version of the same rubber that goes into truck tires! This polymer is a mixture of styrene and butadiene and is abbreviated SBR.

Of the 20 or so chemicals in bubble gum, some dissolve in water and some do not. Most of the water-insoluble portion of bubble gum is called "gum base". That's where the rubber is. Some of the additives in the gum base actually restrict the size to which the bubbles can be blown on purpose, so as not to completely alienate parents! The most intense fragrances and flavorings in fruits are often essential oils like limonene (which is from orange and lemon rinds). They are well suited to gums because they are not water soluble and do not dissolve out of gum in your mouth. Gum does seem to lose flavor after a while, but that is usually because the sugar, which intensifies the fruit flavor, has dissolved.

Sugar Gems. Granulated sugar is made up of ground-up sugar crystals. Have an adult help you slowly and carefully dissolve 2 cups of sugar into 3/4 cup of boiling water. Let the solution cool slightly, and then pour it into paper cups or clear plastic glasses. Set them aside where they won't be disturbed. As the water evaporates, crystals of sugar (sucrose, C₁₂H₂₂O₁₁ ) will begin to form on the bottom and sides of the cup. Unfortunately, the faster the water evaporates, the smaller the crystals will be. Be patient. Crystals the size of peas will form in a month or so, depending on the temperature and humidity. You can buy jewelry settings at a craft store and attach your best gems singly or in groups. If you want to grow large single crystals, you'll have to use special techniques described in books on crystals at the library.

You can prove that this droopiness is due to a gas leak by doing the following test. Get a regular balloon, a bottle of vanilla extract (or almond or orange), and a glass of water. Pour two capfuls of the vanilla into the balloon and then blow it up with air and tie it. Set the balloon on the glass so that the knot is under water. Leave this set-up overnight in a confined space, such as a closed bathroom or closet. Your nose should then help you solve the mystery. A balloon's surface has lots of tiny holes that can be seen only with powerful magnifiers, and vanilla molecules are small enough to eventually leak through this surface. Helium molecules are much smaller than air or vanilla molecules, and so they leak out even faster.

The colors of construction paper quickly disappear with the application of bleach. The trick is to apply and spread bleach in a manner that will result in an artistic pattern. Pour a small amount of bleach into a glass, and then experiment with different applicators, such as a spoon, brush, and cotton swab. Spread the bleach around on the paper by folding, tilting, and blowing through a straw. A little bit of bleach goes a long way, and you'll be able to see the patterns almost immediately. Let your work of art dry before hanging it up for all to see.

In this case the bleaching action can also be called an "oxidizing" reaction. You can prove that oxygen is made from bleach by putting two small balls of steel wool (of the same size) into two different glasses. Cover them with equal amounts of water. Add a tablespoon of vinegar to each glass, and then to just one of them also add a tablespoon of bleach. After about half an hour the steel wool without bleach should be unchanged, but the ball with the bleach should be very rusty. Rust is iron (from the steel wool) that has combined with oxygen in the presence of water. While iron rusts easily, it happens very quickly here because the bleach is producing so much oxygen!

The "cold light" given off by living things is called bioluminescence. Certain kinds of moss glow in the dark, and rotting tree stumps give off an eerie light that is called foxfire. Many cases depend on bacteria. The flashlight fish, for example, lives very deep in the ocean where it is absolutely dark. They have sacs of luminous bacteria near their eyes. The bacteria glow all the time, but the fish can cover and uncover the sacs with flaps of skin. They search for food with these lights, blink to attract other flashlight fish, and confuse their predators by flashing and then quickly changing direction.

Bacteria and fireflies make their cold light by mixing chemicals called luciferin, luciferase, oxygen, and ATP (adenosine triphosphate). This reaction has even been developed into a sophisticated medical test for treating tuberculosis (TB). Saliva samples taken from TB patients are treated to make luciferase and then luciferin is added to make them all glow. Each sample is then exposed to a different antibiotic until the right one works, the bacteria are killed, and the glow goes out.

First, put a piece of bread and a teaspoon of water into a ziploc plastic bag, seal it, and let is sit at room temperature for 3 or 4 days. You'll notice that the bread is now covered in green mold. Mold is a furry growth of fungus found on the surfaces of decaying food or in moist, warm places. A fungus is a tiny non-flowering plant with no chlorophyll, roots, stems, or leaves. The fungus could have gotten onto the bread by a variety of means, such as transfer from your hands.

Secondly, we'll do a test for microbes that cause feet to smell bad. Feel smell bad when very tiny plants or animals grow on our skin. Have an adult boil 1/2 cup of water. Sprinkle in 4 envelopes of unflavored gelatin and dissolve it. Pour this into a clean mayonnaise jar and set it on its side (let the extra pour out and dispose of it). Put on sneakers without socks and go play outside. After about 3 hours the gelatin should be hard and your feet should be smelly. Take a swab and rub it between all your toes. Carefully brush the gelatin with the cottin tip in long strokes. Close the jar and put it in a warm dark place for 4 days.

Where does that pressure come from? At the surface of the water, a column of air weighs 14.7 pounds per square inch, or "one atmosphere". When you go underwater, you add the weight of the water to the atmospheric pressure. A 10-meter (33-foot) column of water also weighs 14.7 pounds per square inch, so at a depth of 10 meters the pressure is two atmospheres: half from the water and half from the air above it. Pressure influences how divers use air. At ten meters, the increased pressure means that lungs hold twice as much air as they do at the surface - and divers breathe air from their tanks twice as fast. This is why divers can stay down only a short time, for example, 15 minutes at 50 meters.

"The bends," or decompression sickness, is a health hazard associated with pressure changes. The longer you stay down and the deeper you go, the more nitrogen gas dissolves into your body tissues. Nitrogen comes from the air we normally breathe, which is about 80% nitrogen and only 20% oxygen. If you ascend too rapidly, the dissolved nitrogen comes out of solution too quickly and forms bubbles in your tissues. You could experience severe pain in joints, dizziness, blindness, paralysis, and convulsions.

It is between the layers or sheets of a clay that chemistry can take place. Many molecules are soaked up into these layers and are either strongly held or else react to form different molecules. Did you know that kitty litter is almost 100% clay? The absorbent properties of clays are obvious here, and they are especially good at binding up the smelliest molecules! Clays are sold commercially as products to help clean up spills, especially oily spills. You will come into contact with kaolinite clay many times a day, for it is used as both a paper filler and paper coating. In fact, the higher quality and glossier the paper is, the more kaolinite is coating the surface; and it aids in binding the inks and dyes. Kaolinite is also the active ingredient in Kaopectate®, and so clay is even used as a dietary aid

What different kinds of glass are there? Huge windows are called float glass because of the way they are made. Since they need to be perfectly flat and smooth, the molten glass is floated on a layer of molten metal (often zinc) and is then cooled very slowly. To visualize this, pour some cooking oil over the back of a spoon onto water in a clear bowl. See how the oil layer floats on top? Some other types of glass are made from other ingredients added to the silica. "Pyrex" cookware is borosilicate, made with some boron to withstand quick temperature changes. Lead crystal incorporates lead to sparkle and make the glass easy to cut and engrave.

What do you know about glass recycling? Amber and green glass are separated because a coloring agent has been added that cannot be removed. Therefore, brown bottles can only make other brown bottles. Recycled glass is crushed into pieces called cullet. Cullet, which melts at a lower temperature, is mixed with the raw materials silica, soda, and lime. This process reduces air pollution by 20%, water pollution by 50%, and saves space in landfills. However, only about 10% of the glass used in the U.S. is recycled.
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Written by: Kathleen A. Carrado, Chair of the Elementary Education Committee.