ChemShorts for Kids   --   2000
Copyright ©2000 by the Chicago Section of the American Chemical Society

by Dr. Kathleen A. Carrado, Argonne National Labs

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

January, 2000

Kevlar: The Millennium Molecule

Kids, last month we learned about teflon and this month we'll learn about another amazing polymer (which is actually a really, really big molecule) called Kevlar. Kevlar is also called the "fabric of steel" because of its outstanding strength. Underwater, it is 20 times stronger than steel! Since its introduction in 1971 it has been used in bulletproof vests and helmets, aircraft, sports equipment, gloves, boats, flight jackets, brake linings, windsurfing sails, cables, even as part of the Orbiter 3 balloon that circled the globe last March.

Last month we learned about polymers in general. Here you'll learn that the secret to the strength of Kevlar lies in something called hydrogen bonding. The long chains of kevlar polymer molecules are stacked like uncooked spaghetti in a box. But the attraction between hydrogen and oxygen atoms on chains next to each other (this is hydrogen bonding) is very strong, and it holds the chains solidly together. Imagine if you moistened the box of spaghetti just enough to make the strands stick together like glue. It is also a bit like the attractive force in static electricity where (a) electrons are relatively easy to remove from atoms and (b) some materials (or atoms) attract electrons better than others.

Here is an activity to mimic this bonding: tear off a strip of scotch tape (which is a plastic or polymer, by the way) about the length of your finger and fold a little bit of one end down so that it sticks to itself. Press it down on a desk top. Tear off another piece of tape, fold a tab as before, and press it down on top of the first piece with the little folded parts together. Rub the top piece several times so that they are well stuck together. Now peel them off together, grab the folded parts and quickly rip them apart. Bring the two pieces slowly near each other, without touching. What happens? The pieces of tape should be attracted to each other because electrons moved toward one side of each tape, leaving the other sides deficient, and the opposite charges attracted.

Dr. Stephanie Kwolek was the chemist at DuPont who discovered the precise chemical concoction needed to prepare Kevlar into useful fibers for making things. At the time, DuPont was looking for a material to replace steel in radial tires (why do you think they would want to do this?). Dr. Kwolek's most satisfying reward for her work has been recognition by the Kevlar Survivors Club. These 2,300 members are police officers whose lives have been saved by wearing Kevlar armored vests. For lots more info about Kevlar please look at the references below.
References: "ChemMatters" 10/99, p. 7 by Peter Banks; American Chemical Society, Washington, DC;; or, look up "aramids" on

February, 2000

Crayon Chemistry

Kids, did you ever wonder what crayons are made of and how all those different colors arise? You probably know that they are "wax" crayons, but let¹s go a little bit deeper than that. Waxes are a mixture of chemicals called esters, fatty acids, alcohols and hydrocarbons. They are for the most part natural substances and are either "animal, vegetable or mineral" in origin. There are many different kinds such as beeswax (animal), carnauba (plant), and candelilla (plant). And then there is paraffin, obtained from petroleum (or "mineral"), from which crayons are made. Paraffin in chemical terms is a straight chain hydrocarbon: one molecule has 26-30 carbon atoms in a row with 2 or 3 hydrogen atoms attached to each. Add a little color (dye or pigment) and presto, you have a crayon.

We urge you to visit a fantastic crayon empire called The Crayola Factory in Easton, PA (610-515-8000) where you can watch crayons being made. The paraffin is delivered to them in heated tanker-train cars and stored in two-story silos. When needed, the wax is pumped into large, heated kettles and mixed with pigment. This crayon mixture is pumped into a rotary mold machine that has thousands of crayon shaped holes, and chilled with cold water. An Instron testing device is used to check the barrel and tip strength of crayons because a strong crayon is a better crayon (sometimes kids grab crayons by the handful or press too hard when they draw or color).

All Crayolas contain the same amount of paraffin wax blend. But their density depends on the amount of color pigments added. Therefore, some crayons will float in water while others will not, and some will sink faster than others. Find out for yourself by performing your own experiments (although we won¹t be responsible for actually telling you to dump your whole box of 96 colors into a bathtub?). No one is saying what pigments are really used because that information is top secret. Some examples for reds might be ocher (an iron oxide mineral), carmine (from an insect), or madder (from a plant). All we can be sure of is that several different pigments are used and that they are all non-toxic. If you are interested in recycling, can you think of a way to re-use your broken crayons instead of throwing them away? One thing to try, with the help of an adult, is to put all the broken pieces into an empty soup can and put this into a shallow pan of water on the stove. The adult can then heat the water enough to melt the crayons, and pour the warm wax into a new mold of some type.

Fun Facts: The average American kid uses 730 crayons by the age of 10. Red and blue are the two favorite colors worldwide. Sulphur, a yellow-green combination, is the most disliked color in the world. The name Crayola ("oily chalk") is from the French word "craie", which means chalk, and "ola" (from oleaginous), which means oily. Although there are 96 different Crayola colors, there are only 18 different label colors. Among the 20 most recognized smells in the world, crayons placed 18th (first was coffee, followed by peanut butter).
References: The Crayola Co.¹s website at

March, 2000

The Chemistry Behind "Magic" Pens

Kids, let¹s look at the cool chemistry that makes color-changing markers work. These special colored markers are used to make colorful masterpieces, and when they are drawn over with a special white marker the colors change. Let¹s be investigative about this and look at the science of this rather than the magic. You¹ll need a marker set, Q-tips, a 4 x 6" index card, white vinegar, a baking soda solution (dissolve 3 tsp of baking soda in a cup of distilled water), distilled water, 3 plastic cups, and a red cabbage leaf.

Place your index card the long way (vertically) on a table with the blank side up. With each of three magic pens, draw parallel, horizontal lines about 2 inches long and about 1/4 inch wide, separated by about half an inch or so. Add a fourth line by bunching up the red cabbage leaf and rubbing it until you see a streak of color on the card. Using the white color-change wand, draw a straight, vertical line (perpendicular), that crosses all four color lines. Label it "wand". Now pour a little bit of water, vinegar, and baking soda solution into three separate plastic cups. Using new cotton swabs for each solution, dip in and "draw" the wet swabs across all four color lines as before, labeling each one.

Describe and compare the effects that the wand, water, acid (vinegar) and base (baking soda) solutions have on all of the colored lines. Are the pens sensitive to acids or bases? Here is one example of using the pens: draw a line with the color-change wand first, then draw across it perpendicularly with a blue marker. It¹ll be blue on either side of the wand path, but a different color (turquoise), where it crosses the path. The low pH color (blue) is observed where there is no base (ink from wand), and the high pH color of turquoise appears on the base¹s path. (Remember, high pH means basic and low pH means acidic).

Here is the chemistry behind the "magic". Like many pens, the ink used here is composed of many parts. The magic pen ink contains deionized water, glycol as a humectant (substance that retains moisture), a non-sudsy detergent (to help spread liquid on a surface), citric acid (the acid in lemons and orange juice) to create a low pH, and a dye. The color-change wand contains water, glycol, and detergent, as well as a base (such as sodium hydroxide), and a reducing agent (such as sodium sulfite). Because of the base, it¹s pH is about 10-12 depending on the brand.

Each colored marker actually has two separate dyes. One dye becomes colorless at high pH in the presence of a reducing agent. The other dye is not affected by either. When you draw with a colored marker, you see a particular color. When the color change wand is drawn over that color, one of the dyes disappears (turns colorless), leaving the other color for you to see. Some clever chemists have used simple chemical reactions based on acid-base and oxidation-reduction chemistry to make these wonderful pens work.
References: C. Anderson and D. Katz, ChemMatters, American Chemical Society, 10/98, p. 4.

April, 2000

A Shape Memory Metal

Kids, did you ever imagine that there might be chemistry involved in braces? How about eyeglass frames? There is a special metal alloy called Nitinol that is often involved in both of these applications. It is a nickel-titanium (Ni-Ti) alloy developed by chemists at the Naval Ordinance Lab (NOL) ­hence the name of NiTiNOL. This unique metal displays the very rare phenomenon of the shape memory effect. It seems to remember its original shape after being bent.

Let¹s see how it works in braces. The bracket part of braces is a tiny metallic or porcelain anchor glued to a tooth. As many as 12-14 of these minihandles are fastened in each jaw. Next a thin flexible Nitinol wire is fastened to each bracket and bent back and forth as necessary to connect the misplaced teeth. This special wire is elastic (actually, "superelastic") and wants to, very slowly, return back to its original straight shape. Moving at about one millimeter per month, the wire brings the teeth with it. Eventually, a stronger stiffer wire is needed to move teeth into their permanent final alignment, and orthodontists often use stainless steel for this. Both Nitinol and stainless steel (an alloy of iron and carbon with some chromium and nickel) are resistant to acids and corrosion. You never see rust on braces even though they are in a wet environment and exposed to weak acids (citric acid, decomposition of sugars, etc.).

Another example of Nitinol¹s properties is in the springs of eyeglass frames whose arms can flex slightly out, away from the body, without damage. One of the most amazing demonstrations of shape memory is when it is temperature dependent. Nitinol can do this as well. A straight wire can be wound into a tight coil, put into hot water, and instantly it springs back to its straight shape. Eyeglasses with this Nitinol in the temple piece can be squashed or severely bent, but restored by immersing in hot water. This effect is caused by a change in the crystal form of the metal. It transforms between the high temperature phase called austenite and the low temperature form called martensite. Because the phase change occurs with just a simple shearing motion of the atoms, and no diffusion or large atomic movement is required, the transformation occurs virtually instantly and can cycle many times.

Most applications of Nitinol are in aerospace engineering and hydraulics. For $35, Shape Memory Applications, Inc. will supply a kit of demo wires and springs (2380 Owen St., Santa Clara, CA 95054, (408) 727-2221; The demo wire is especially fun ­ bend it, dip into hot water, and bam! it snaps back to straight, over and over again. Their website also has a very helpful review document. Also published for demo purposes is the "Thermobile" (G. Kauffman & I. Mayo, J. Chem. Educ. 1998, 75(3), 313), an engine with no visible power source that converts thermal energy to mechanical energy using a Nitinol loop wrapped around two pulleys. I encourage you to research this amazing metal. Some other alloys showing this effect are gold-cadmium (Au-Cd) and brass (copper-zinc).
References: M. W. McClure, ChemMatters, American Chemical Society, 2/00, p. 7.

May, 2000

Pictorial Guide to Molecules

Kids, here's a really cool guide to what some common atoms and molecules look like when we have a whole bunch of them together, and see their everyday appearance.

You need to have a special program, called Adobe Acrobat Reader, to see this chart. If you don't already have it, you can download in a copy for free with your parent's help by clicking here. If you already have Acrobat Reader, or have just loaded it onto your computer, you can see the chart by clicking cool chart.

June, 2000

Testing the Texture of Toothpaste

Kids, chemistry is so common that it can even be found in toothpaste. Chemists have worked hard to come up with the perfect stuff. Read the labels – you'll find out all kinds of interesting things. Here you'll find some information plus learn some tests you can do to compare different brands.

What are the active ingredients in toothpaste? There is fluoride of course, either as sodium fluoride or sodium monofluorophosphate. Fluoride reverses the process of tooth decay where acids (especially from sugar) dissolve minerals right out of the teeth. There are antibacterial agents such as triclosan to control plaque and antitartar agents to control mineralized plaque. Other, inactive or inert, ingredients are water, detergents (to loosen plaque), binders (keeps solid and liquid ingredients together), humectants (to keep it moist in the tube), flavoring, preservatives (to stop bacteria from growing on the other stuff), and abrasives (for cleaning and polishing).

Using the tests that follow, you will use inquiry to observe, collect data, and make informed decisions related to consumer choices. You'll need toothpicks, 4-5 brands of toothpaste, a toothbrush, and also a microscope would be great. Prepare a chart listing the brands of toothpaste with sections for texture by "touch", "taste", and "microscope". Rub a bit of each brand between your fingers and note whether it feels smooth, gritty, etc. Then brush your teeth with each brand and record the texture by taste. Next, using a toothpick, smear some toothpaste on a microscope slide, add a drop of water, and put on a coverslip. View the slide in a microscope and draw a picture on your chart of what it looks like. Now compare all the brands for texture, grit, and appearance. Which would you choose, and why? Why is this better than just using water to brush your teeth?

What do you suppose the abrasives are? This grit is often silica, alumina, calcium carbonate or sodium bicarbonate. Chemists are able to make toothpaste clean, polish, and protect your teeth, plus make it taste good and sit up on your toothbrush, too!

October, 2000

$$   The Science of Money   $$

Kids, chemistry is so common that it can even be found in money. Here we'll learn some science about coins and bills. Let's talk about coins first. Pennies obviously look different by their color while all the rest appear to be the same silvery color, until the new 2000 "golden" Sacagawea dollar coin came along. Have you ever thought about what metals are used to mint these coins? All the silvery-looking coins are actually made out of copper with small amounts of nickel. This nickel amount can be as low as 8% (dimes, quarters, and half dollars) to as much as 25% (nickels). Makes sense that the most is used for the nickel, right? The new gold dollar is really made of "manganese-brass", which is 88% copper, 6% zinc, 4% manganese, and 2% nickel. The penny has seen quite a few changes over the years. It was pure copper way back in 1793-1837. For the next 20 years, it was bronze (95% copper, 5% tin+zinc). Then even this small amount of tin was removed in 1962. In 1982, pennies became copper-plated zinc coins, with a thin coating of Cu (2.5%) over a pure zinc core.

Have you noticed that some coins have grooved edges? Dimes, quarters, half-dollars, and dollars used to contain precious metals like gold and silver. Grooved edges helped stop counterfeiting. It also stopped the filing down of edges by people who were collecting (actually stealing) the precious metals. Even though coins no longer have such metals, grooved edges are kept because they help the visually impaired to identify them. The chemical element symbols for all of these coinage metals are: copper (Cu), nickel (Ni), manganese (Mn), zinc (Zn), tin (Sn), gold (Au), silver (Ag).

Did you know that "paper" money is actually made of 1/4 linen and 3/4 cotton? This makes it more like fabric than paper and explains why it's washable. There are many counterfeiting-fighting features used, especially on the new "big head" bills, but we'll mention only a few here. You notice of course that the portraits are enlarged and off-center. This allows for a watermark, which is another portrait visible when held up to bright light. The watermark is formed by varying paper density in a small area during the papermaking process, and does not copy on color copiers or scanners. A security thread appears in a different location on each new denomination. When held to a light you can see "USA TEN" or "USA TWENTY", etc., and flags in this thin thread. When viewed under ultraviolet light, the thread glows different colors. For $5 it is blue/purple, $10 is orange, $20 is a bright green, $50 is yellow, and $100 is pink-red. These colors arise from various fluorescent dye molecules used in the inks. Finally, for every new bill except the $5, a color-shifting ink feature is used. The number in the lower right corner changes from green to black as the bill is moved. The change in color is the result of multi-layered metallic flakes added to the ink. When the bill is tilted, light reflects off these flakes at different wavelengths and changes colors. This is called color diffraction, which is also responsible for the color variations found on the wings of some butterflies.

Kids, a fairly addictive thing to try on the internet is the site This tracks dollar bills by serial number as they float around the country. Have fun!


References: The Bureau of Engraving & Printing's website at, and the U.S. Mint's website at (both have great kids sections). Also

November, 2000

A Silicate Garden

Kids, have you discovered the colorful rocks that grow into underwater stalagmites yet? The ingredients for making your own silicate or crystal garden are a bit too exotic for you to find around the house or in the grocery store. Your best bet is to go to your favorite toy store and look for a product from Craft House called “Magic Rocks”.

Follow the instructions very carefully. In fact, they say that an adult partner is needed if you are not 10 years old yet. We’ll give you a bit more of a scientific explanation here of what you’ll observe happening. You’ll first place the “magic rocks” into the bottom of a container and then pour a “magic solution” over them. The rocks are actually chunks of chemicals such as iron chloride (FeCl3), cobalt chloride (CoCl2), copper sulfate (CuSO4), manganese sulfate (MnSO4), and iron sulfate (Fe3(SO4)2). Chemists call compounds like these transition metal salts. They are indeed salts but they are not edible so don’t even think about it! The colors of these particular salts are, respectively, yellow, purple, blue, pale pink, and green. There might be different salts, and therefore different colors, in your set. These are just examples. The solution is sodium silicate, also sometimes called “water glass”. What you are making is a structural precipitate and they are quite complex. The iron chloride salt, for example, changes by chemical reaction with the sodium silicate to a mixture of iron silicates and iron hydroxide. This mixture is gel-like. But the gels will change their texture to become more crystalline and brittle after a while.

An air bubble usually caps the slender shoots that form at first, so look carefully. They move jerkily, from one side to another. An elastic gel-like membrane is actually forming and breaking here.

If your set doesn’t seem to work very well it might mean that the sodium silicate solution has degraded a little bit, especially if the set is old. Most transition metal salts shouldn’t be affected by time, though.

December, 2000

Yeast Chemistry - Part I of III

Kids, did you know that yeast is a tiny living fungus and that, like all living things, they need to eat? Here you will make your very own bubbly, gooey yeast for baking bread. The biochemical process is called fermentation, which begins as yeast eats the sugars in fruit and grain. This releases enzymes that decompose the food to make alcohol and carbon dioxide gas. Make a chart to keep track of the daily changes in color, smell, and texture (frothy, pasty, gooey). (Note: don¹t use metal bowls or spoons because metal interferes with the chemistry; wooden spoons are okay).

Remove 10 grapes from their stems, wash well to remove pesticides (which kill yeast), and tie them in a double layer of cheesecloth. Or use unwashed organic grapes. Using your hands, fold 4 cups of lukewarm water and 3-3/4 cups unbleached white bread flour in a large glass bowl until it¹s like lumpy papier-mâché. Swish the grape bag through the mixture and push it to the bottom. Either cover the bowl tightly with plastic wrap or transfer the mixture to a plastic container with a tight lid. Store at 70-75oF. Remove the lid every day to record your observations. Fermentation has begun when you see bubbles and smell an odor. On day 4 you should see a yellow liquid. Any purple or brown spots are beneficial bacteria that also add unique flavor. Feed the yeast a cup of bread flour (which supplies sugar) and a cup of water. Mix well. On days 5-9 watch for any green, fuzzy mold. If it forms, remove it and add another cup of flour and water. On day 10, take out the grape bag and divide the mixture into two-cup "starter" portions. These can be given to friends and relatives, keeping one for yourself.

In a large glass bowl, add one cup of flour and one cup of water to your starter. Mix well. Cover loosely with a towel for about 8 hours. A lot of CO2 gas will be given off here so do not use a tight-fitting lid. Repeat this step and ferment 12-14 hours. Add flour and water in this manner twice a day through day 14. During these feedings the dough should rise as enzymes from the yeast break down the sugars in flour and release CO2 gas that is then trapped in the gooey gluten. In next month¹s column we¹ll bake the bread. If needed you can store your starter in a refrigerator, where it will become dormant.
Reference: Nancy Lang, Scientific American Explorations magazine, Fall 2000, p. 14.

Updated 1/8/01