ChemShorts for Kids   --   1999
Copyright ©1999 by the Chicago Section of the American Chemical Society

by Dr. Kathleen A. Carrado, Argonne National Labs

ChemShorts Home

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

January, 1999

Density Displays

Kids, here you will be introduced to the concept of density, which is one property used by chemists to help identify unknown substances.

Let's first make a liquid sandwich. Begin by getting a clean, narrow jar (a tall baby food jar or baby juice jar, or an olive jar) and adding 3 tablespoons each of vegetable oil, water, and honey or molasses to the jar. Watch and observe what happens. Eventually the honey or molasses will sink to the bottom, the oil floats on top, and the water is in the middle part of the "sandwich". They honey or molasses sinks the furthest because it is more dense (it weighs more for the same amount) than either water or oil. The oil floats because it is the least dense of the three.

Now let's try a density column. Use a large test tube or another clean, empty, tall jar (olive or baby food jar). Add 3 tablespoons each, in order, of water with a drop of red food coloring, then vegetable oil, and then rubbing alcohol with a drop of blue food coloring. Pour these each slowly and carefully, and in the order of water, oil, alcohol. Wa-la, you now have a very patriotic display of your densities!

Finally, to reward you for your efforts, you can try this density display that is good enough to eat. Put a 4-oz box of dry lemon gelatin in a bowl, have an adult add 1 cup of hot water, and stir until the gelatin is dissolved. Add 4-oz of whipped cream cheese (at room temperature) and stir again. It won't blend well but it will break into little bits. Does the cream cheese sink or float in the gelatin? Why? Add 1 cup of cold water to the gelatin and stir. Now add an 8-oz can of drained fruit cocktail and stir yet again. Does the fruit sink or float? Why? Pour the gelatin mixture into four small cups and refrigerate until it sets. Observe changes as they chill. Where do the cream cheese and fruit pieces end up?
Reference: M. Mandell in "Simple Science Experiments with Everyday Materials", Sterling Publ., 1989, p . 76 and ACS "WonderScience", February 1989 issue.

February, 1999

A Viscosity Race

Kids, do you know what lubricants are? They help reduce friction, or wear and tear, between moving parts. They can be solids such as graphite, soap, or talcum or they can be liquids like oils and greases. An important feature of a liquid lubricant is its thickness or ability to flow. This quality is called viscosity. Look up viscosity in the dictionary and it says, among other things: "the property of being glutinous or sticky". Well this certainly sounds like it could be a fun property to experiment with. It is the job of chemists to create and analyze lubricants. But you can easily tell which ones are more or less viscous than others by doing this simple experiment.

You will need 3 tall, narrow, clear jars with lids (olive jars or baby food juice jars), vegetable oil, clear shampoo, clear dish detergent, and 3 chocolate chips. Nearly fill one jar with the oil, one with the shampoo, and the last one with the detergent. Make sure all the levels are the same. Gently place a chocolate chip in one of the liquids. Time how long it takes to reach the bottom with a stopwatch. Make a chart and record the time. Do the same thing with the other two chips and liquids. Or, you can make a race out of this with two friends. Place the chips in the liquids at the same time and see whose goes fastest and slowest.

Determine which liquids have the shortest time, the next shortest time, and the longest time. For the jar with the shortest time for the chip to reach the bottom, is the liquid in that jar more viscous or less viscous than the other liqudis? Hint: the longest time = the most viscous liquid.

You can make these jars reusable by sealing the tops on with Kraft glue. If you do this, seal a different colored marble into each jar rather than a chocolate chip.
Reference: "WonderScience" March 1990 issue and M. Ebeling (primary level teacher, Naperville district 203).

March, 1999

Color Drops

Kids, let"s watch the ways in which food coloring can move through different liquids. You"ll need 3 clear plastic cups, water, 4 teaspoons of salt, seltzer water, and food coloring.

Fill two of the cups 2/3 full with water. Add 1 drop of food coloring to the first cup and immediately observe what happens. You can use a worksheet to draw your results. To make the worksheet, first draw three simple cup shapes on the paper, indicate the liquid level by drawing a wavy line 2/3 of the way up, and label them plain water, salt water, and fizz water. Add the salt to the second cup and stir until the salt dissolves. Add one drop of food coloring to the this cup and immediately observe, and again draw what you saw. Now fill the third cup 2/3 full with seltzer water, add 1 drop of food coloring, observe, and draw.

What happened? In plain water the drop slowly swirls and moves throughout. In salt water, the drop starts to sink and then rises. In the fizz water, the drop quickly disperses and evenly colors the liquid. Why? Putting food coloring in plain water does not have a dramatic effect other than that the color becomes more pale (diluted). The gas bubbles in the fizz water act to speed things up, like an invisible stirring spoon. The drop of food coloring is quickly broken up and carried to all parts of the liquid. Salt water is more dense than plain water. This means that anything less dense will float on the top, including the food coloring (which is a drop of colored water).
Reference: Marlisa Ebeling (primary level teacher, Naperville district 203).

April, 1999

Cabbage Chemistry - pH Tests

Kids, let's make your own acid/base pH indicator by doing a little cooking - just by boiling red cabbage. The juice is used to test the pH of different liquids. Tear up 1/2 head of red cabbage (or use a grater with supervision), place the pieces in a pot and add just enough water to cover them. Boil (with supervision) for 20-30 min until the liquid turns a dark purple color. Let cool and pour through a strainer into a large jar. You can even save the cabbage for later - add a little vinegar and it's a relish for hotdogs, etc. The collected liquid should be blue/dark purple. Make some test acid and base solutions in cups: white vinegar, clear soda, diluted lemon juice (acids) and some detergent in water or some baking soda in water (bases), and pure water (neutral). Add a few drops of the cabbage juice to each solution and note any color changes.

The juice should turn pink in acidic solutions, green in basic solutions, and not change in neutral solutions. Try some other solutions of interest. You can also try making your own pH paper: soak a coffee filter in the juice and let it dry, then cut into test strips. Or pre-cut the filter into any interesting shape. Dip your papers into the test solutions are record what happens. What might happen if you dip a paper first into a base and then into the vinegar? You can even try a little creative art by using a cotton swab dipped in vinegar to draw on your pH paper. Can you then make your art disappear? Try all of these things and have fun!

Further comment: Red cabbage works so well because of the highly colored anthocyanin dye it contains. Other plants that contain these molecules are beets, cranberries, and blueberries.
References:, the
Mad Scientist Network based at Washington University Medical School in St. Louis, and WonderScience, February 1988.

May, 1999

Epsom Salt Towers

Kids, can you say "super-saturation"?   This is a big word but by using the principle behind it, you can make some cool formations. Follow me...

You'll need to measure 2/3 cup of Epsom salts into 1 cup of hot tap water (have an adult do this) and stir.   Divide the solution into two small clear glasses or jars.   Put a large paper clip onto each end of a 12-inch piece of cotton string.   Soak the string for 5 minutes in one of the solutions.   Spread aluminum foil on a work surface, and hang the wet string between the two containers.   The paper clips will weight the ends down in each glass or jar.   The glasses will be about 4-6 inches apart.   Let the string hang with a little slack between the two glasses.   After about 30 minutes, you should see a tower growing down from the string (a "stalactite"), and a tower growing up from the table under the string (a "stalagmite").  Let it go overnight to see how large your towers can grow.

What's happening here?   The solution you made was supersaturated - which means that there is more magnesium sulfate (which is what epsom salts is) dissolved in the solution than in possible at regular temperatures.   How can that be?   Remember that you used hot water, which lets more MgSO4 (which is another way of "saying" magnesium sulfate...) dissolve.   As the solution drips from the string, the water evaporates.   This leaves the MgSO4 behind to solidify into your towers.  In other words, we see the results of an evaporation process as the MgSO4 crystallizes.

Think about a place where you might have seen such formations but on a much grander scale.   Were you ever in a cave that had stalactites and stalagmites?   These towers are usually made of calcium carbonate (limestone) rather than magnesium sulfate, but they form in much the same way - by evaporation of water from solutions containing a lot of calcium and carbonate ions.   We hope you learned a lot of chemistry today, from the physical processes of supersaturation, evaporation, and crystallization, to some of the geochemical processes that occur in caves.   Try out this experiment and then go visit a cave this summer - happy spelunking!  (another big funny word...we dare you to look it up).

References: "Planet Chemistry" from the American Chemical Society's National Chemistry Week Office, 1997 (

September, 1999

The Incrediblob

Kids, now it's time to use chemistry to make your own plastic ball. Cover a work surface with two layers of paper towels. Into a small plastic cup put one tablespoon of white liquid glue (like Elmer's®). Into another small cup put 1/2 teaspoon each of Epsom salts and water. Swirl the cup until no more Epsom salts will dissolve (if any is left undissolved at the bottom of the cup that's okay). Pour all the contents from the Epsom salts cup into the glue cup and stir it up with a plastic spoon. What happens to the mixture?

Scoop the mixture out onto the double thickness of paper towels, fold the towels over it and press down to absorb the extra water. Pick up your newly formed plastic and form it into a long roll. See how long you can make the roll without it breaking, and measure it's length. Form the plastic into a ball and flatten it down onto a piece of wax paper like a pancake. See how large a pancake shape you can make that can be lifted off the wax paper in one piece, and measure it's diameter.

Form the plastic back into a ball and try bouncing it off a hard clean surface. Congratulations on making an incredible, incrediblob incrediball!

Chemistry notes: Note how many different plastics you used to help make one of your own (the cups, the spoon). On the day you do this experiment, try to make a list of all the plastics you see that day and you'll be amazed at how long the list can be. Epsom salts are a chemical product called magnesium sulfate (MgSO4). You should have some left over from making the Epsom salt towers described in the last column. Try to work quickly in this experiment because your plastic material will dry out as you use it.


Reference: "WonderScience" from the American Chemical Society, 1991, vol. 5(8), issue on plastics (ACS, 1155 Sixteenth St., N.W., Washington, DC 20036).

October, 1999

Clearly It's Vitamin C

Kids, which has more vitamin C in it: Tang® drink mix or orange juice? Let’s use some chemistry and a color test to find out. Have an adult make an iodine solution by adding 1 teaspoon of tincture of iodine to 1 tablespoon of water in a labeled plastic cup.

Use two 8-oz plastic cups to make a starch solution: dissolve the 4 starch pellets (biodegradable packing peanuts available at mailing supply stores) in 1/2 cup of water. Cover the other cup with a coffee filter in an indented bowl-like shape. Pour the starch solution through the filter and label this clear solution as “Starch”. Label three 3-oz plastic cups as “Vitamin C Test”, “Tang Test”, and “Orange Juice Test”, and put 1 tablespoon of starch solution in each. Now add 1 drop of the iodine solution to each test cup using an eyedropper. What happens? They should all turn blue from the starch/iodine complex that forms.

Label a fourth cup “Vitamin C Solution”. Crush up a vitamin C tablet, put it in the cup, and add 2 tablespoons of water with stirring. Now place 1 drop of this vitamin C solution in its test cup (“Vitamin C Test”) and swirl. What happens? (If nothing happens add another drop). Next mix 3/4 teaspoon of Tang® powder in 2 tablespoons of water in the fifth cup and label it “Tang Drink”. Put a drop of this drink in the Tang Test cup. Does it take more drops to turn the solution clear than vitamin C? Lastly, add 1 drop of orange juice to its test cup. Does anything happen? How many drops of orange juice does it take for this solution to become clear?

So which has more vitamin C in it, Tang® or orange juice? The more vitamin C a solution has, the fewer drops it takes to turn the starch/iodine solution clear. So the fewer drops it takes, the more vitamin C the solution has. Try testing some other drinks for vitamin C, such as calcium-fortified orange juice, orange soda, lemon-lime soda, cranberry juice, or anything that says “ascorbic acid” (another way of saying vitamin C) in the list of ingredients.
Reference: “WonderScience” from the American Chemical Society, 1999, vol. 13(6), issue on chemistry & color (ACS, 1155 Sixteenth St., N.W., Washington, DC 20036).

P.S. The tablet should have the most vitamin C, followed by Tang, and lastly the orange juice (which has the least).

November, 1999

Egg Engraving

Kids, let's use some chemistry to engrave your name on a hard boiled egg. It's actually a process of reverse-engraving, because we'll make all of the shell disappear EXCEPT for your name!

First, your adult partner will have to hard boil some eggs for you (only one is needed for the experiment, but you can always eat the extras). With a china marking pencil or a wax crayon, print your initials or your first name, large and fairly thick, on the shell of a hard boiled egg. Now put the egg in a glass large enough to hold it and add enough fresh white vinegar to cover it. Tiny bubbles should form on the egg which show that the acid in the vinegar is reacting with the shell. The shell under the waxy letters is protected from this acid action. In an hour or two, when the bubbling stops, replace the now neutralized vinegar with a fresh supply. After another two hours wash off the egg under running water. Rub your fingers over the letters and they should stand out in relief.

You can even try to GENTLY remove the wax coating with a soft brush and scouring powder under running water. An average eggshell is .094 inches thick. It's made of 3.5% protein, 1.5% water, and 95% calcium carbonate mineral. It is this CaCO3 mineral that reacts with the acetic acid in vinegar. If half of the shell has dissolved during the four hours, then it has only about an .05 inch-thickness left. So Be Careful!

If you are interested, the very first ChemShorts column (published way back in January 1992) was called "The Naked Egg" and tells you how to completely dissolve an eggshell. Click here to see this ChemShort

Reference: "Mr. Wizard's Supermarket Science" by Don Herbert, Random House: NY, 1980, page 41.

December, 1999

Teflon: A Guiness Record Holder

Kids, did you know that teflon is listed in the Guiness Book of World Records as the slipperiest material in the world? The secret lies in its highly stable covalent bonds. Let¹s learn more about teflon's chemistry and do a little test of its amazing properties.

Teflon is a polymer with long chains of strong carbon-carbon bonds. The long chains are strung together from short tetrafluoroethylene (C2F4) molecules. The tradename teflon is actually a short version of the chemical name polytetrafluoroethylene (PFTE). Each carbon in the chain also has two fluorines attached to it, and C-F bonds are exceptionally strong. The C-F bonds are so strong that virtually nothing can break them apart. Not other chemicals and not high temperatures. It is therefore perfect for nonstick coatings on cookware.

Try this test using teflon tape. PFTE tape is available in most hardware stores because plumbers use it to make water-tight seals between threaded pipes. Cut a 10-15 cm length of this tape and stretch it a bit lengthwise. Now stretch it a little bit widthwise and note the difference. Now stretch it again lengthwise and note what happens. Cut a new length and with a permanent marker carefully print your name on the tape. You'll have to write very lightly and hold the ends tightly (perhaps a friend can help) because the tape will want to bunch up. It's tricky but you can do it if you're careful. Slowly stretch the tape widthwise in a few places to distort your name beyond recognition. Now pull the two ends apart and voila! your name will appear again. Redistort and try again. Think about the properties of teflon tape that let you do this. A common question is: if nothing sticks to teflon, how can teflon stick to a pan? DuPont uses a procedure (called stratification) in which a mixture of materials is baked onto a metal pan at a high temperature (about 420°C). During this treatment, binder molecules in the mixture attach to the pan, and the fluoropolymer molecules rise to the top of the coating. The result is a non-stick surface that stays in place. Check out for details on the development of teflon and other applications. Next month: Kevlar!
Reference: "ChemMatters" 10/99, p. 16, by R. Becker; American Chemical Society, Washington, DC.

Updated 10/24/99