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

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.

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.

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!

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).

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.

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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.
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Reference: “WonderScience” from the American Chemical Society, 1999, vol. 13(6), issue on chemistry & color (ACS, 1155 Sixteenth St., N.W., Washington, DC 20036).

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!

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.