ChemShorts for Kids   --   2001
Copyright ©2001 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, 2001
Yeast to Bread ­ Part II of III

Kids, did you make your own yeast according to last monthıs column? It is really fun chemistry to do hands-on and it has a biological slant (in a word, "biochemistry"), so we hope that you did. If you had to refrigerate your starter yeast in order to wait for this column to appear, remove one cup of it and feed it for a few days, twice a day, as you did on days 11-14 before. Now you are ready to start a "Sweet Friendship Bread". In a glass bowl mix 1 cup each starter, vegetable oil, and sugar, 4 eggs, and 2 tsp vanilla. In another large glass bowl mix 2 tsp baking soda, 1 tsp baking powder, 2 cups flour, 2 tsp cinnamon, and 1 cup each chopped pecans, chopped apples, and raisins. Blend every-thing, mix well, and pour into three 9x5" loaf pans. Have an adult partner bake it for 50-60 min in a preheated 350oF oven.

Yeast cells digest food to grow. Their favorite food is sugar, either sucrose (cane sugar), fructose and glucose (from honey, molasses, and fruit) and maltose (from starch in flour). Glucose is C6H12O6. This fermentation process makes carbon dioxide and ethyl alcohol. Flour Facts: When mixed with liquid and kneaded, flour develops enough gluten to support the carbon dioxide made by the yeast. Gluten is the elastic molecule formed when the protein of flour meets a liquid. Kneading makes the gluten stronger so it can hold in the gases formed by the yeast. This recipe didnıt call for kneading, but many do. After baking the dough youıll see the remains of the CO2 gas bubbles as air pockets in the bread. Fat Fact: Fats like butter, margarine, and oil are used in breads to make the gluten strands slippery so the yeast gases can expand easier. Liquid Facts: Breads made with water will have a more open texture, a more wheaty flavor, and a crispier crust. Milk creates breads that are richer with softer texture; crusts are softer and will brown faster due to the sugar and butterfat in milk. Sugar Facts: Sugar provides food for the yeast to grow and adds flavor. Salt Fact: Salt controls the speed at which the dough rises. In next monthıs column weıll do more experiments with yeast, so stay tuned!
Reference: Nancy Lang, Scientific American Explorations magazine, Fall 2000, p. 14 and   See for a peanut butter bread recipe with Fleischmannıs yeast.

February, 2001

Experiments with Yeast ­ Part III of III

Kids, did you make your own bread from yeast according to the last few columns? We hope you did, but if not you can still do quite a few experiments with store bought yeast. The first experiment here tests how sugar effects the growth of yeast. Fill two 1-cup glass measuring cups with 1/2 cup warm water. In one cup, add 1 tsp sugar. Put 1/4 ounce package of active dry yeast in each cup, stir, and wait 10 minutes. Which cup has more yeast foam and why? Is sugar necessary for the growth of yeast and why?

Is yeast alive? Make a yeast solution using 1/2 cup warm water, 1 tsp sugar, and 1/4 ounce package active dry yeast. Each day, transfer 1 tsp of original yeast solution to a solution of 1/2 cup warm water and 1 tsp sugar. Make another sugar solution and add 1 tsp water daily. Keep a record of observations for five days. Does the yeast culture continue to multiply even though it is diluted by the daily transfer?

When flour, sugar, water, and yeast are mixed, what happens? Get two empty 1-liter soda bottles and two balloons. Fill each soda bottle with a 1/4 ounce package active dry yeast, 1 tsp sugar, and 1 cup room temperature water. In one bottle, add 2 Tbsp all-purpose flour. Secure a balloon on top of each soda bottle. Record and time what happens to the balloons. What is the difference between them? Does flour make a difference in the length of time the fermenation works and why?

What effect does temperature have on the fermentation of yeast? Again get two empty 1-liter soda bottles and two balloons. Fill each bottle with a 1/4 ounce package active dry yeast, 1 tsp sugar, 2 Tbsp all-purpose flour, and 1 cup room temperature water. Set one bottle in a vessel with warm water. Set the other bottle in a vessel with ice water. Secure a balloon on top of each soda bottle. Observe and record results. What effect does temperature have on the fermentation of yeast? When was the difference most noticeable? Read over the last two columns for interesting facts concerning yeast and they will also help you answer the questions asked here.


Reference: ("The Science of Yeast" webpage). For microscopic photos of budding yeast cells check out: or

March, 2001


Kids, baking soda and/or baking powder are added to cooking batters to produce the gas bubbles that make cakes and muffins rise (this is called "leavening"). It is caused by the action of baking soda plus a liquid acid. Baking soda is sodium bicarbonate (NaHCO3). When mixed with a liquid acid it releases the gas carbon dioxide (CO2). Of course you've seen this - when you mix baking soda with vinegar it fizzes with CO2 bubbles. Recipes that use baking soda for leavening always have an acid somewhere, like vinegar, lemon juice, or buttermilk. Less obvious acids are those in honey and molasses.

Baking powder is a combination of baking soda plus a dry acid. When baking powder is mixed in a batter, the dry acid and the baking soda can react together and release CO2. Dry acids are certain tartrates, phosphates, or sulfates. Double-acting powders are the most common. The first "action" is the release of CO2 when one of the dry acids dissolves in liquid and reacts with the baking soda. The second "action" is the release of CO2 when the batter is heated in an oven. This relies on a different acid that dissolves only at higher temperatures.

EXPERIMENT 1. The purpose here is to determine if CO2 is released when baking soda and baking powder are added to water. Dissolve 1 tsp baking soda in one cup of water and 1 tsp baking powder (a double-acting one) in another cup of water. The baking soda should dissolve without fizzing and the baking powder should fizz. Why? Note also that the baking soda dissolves completely but that the baking powder solution is cloudy. Look at the label and youıll see cornstarch is an ingredient. One possible explanation is that cornstarch doesn't dissolve. A follow-up experiment with 1/2 tsp cornstarch a glass of water will confirm this.

EXPERIMENT 2. The purpose here is to determine whether baking soda and baking powder will fizz when acid is added. So, add 1 tsp of vinegar to the solutions from Experiment 1. We expect that when the vinegar (acetic acid) is added, CO2 gas bubbles will be released from the baking soda solution but not from the baking powder or the control cornstarch solution.

EXPERIMENT 3. The purpose here is to determine whether baking soda and baking powder solutions will fizz when heated. Prepare one cup of water each with 1 tsp baking soda, baking powder, and cornstarch. After the baking powder stops fizzing, ask an adult partner to microwave them all for 1 minute (in microwave safe containers). Only the baking powder solution should fizz upon heating. In this the other dry acid (probably sodium aluminum sulfate, or alum) dissolves as the product is heated. As it dissolves, more is in solution to react with the bicarbonate.

Think about all these reactions occurring the next time someone bakes you a cake. This is inorganic chemistry in action!



April, 2001

ChemLinks for Kids

Kids, in this column weıll put together some of our favorite internet sites for chemistry experiments and learning activities at the elementary school level. This is so that you have something to do in between our monthly columns! One of our favorite resources through the years has been the American Chemical Society magazine WonderScience. It is now published solely on the web at Activities investigate topics in science through fun, safe, and easy experiments using inexpensive materials found in the home or grocery store.

A very appealing and information-loaded site is hosted by Within their "Education" link is an "On-Line Educational Resources (SLN)" link to such on-line activities as pH and "The Atoms Family", which deals with energy concepts. Both feature highly interactive portraits that are just right for K-5. The Minnetonka Science Center is loaded with teacher tools and ooey, gooey recipes for K-5 science (Gak, Oobleck, Slime, even a singing cake). Start at and proceed to "Teacher Information". This site also contains useful science fair information. Check out the lesson plans at this science connection: They include density of cereals, crime scene investigations with paper chromatography, and oobleck and glurch, all for grades 3 and up. Now that youıve made some Oobleck, hop to the Jefferson Labs site for ideas on what to do with it: and click on the "BEAMS" program for grades 6-8 activities. There are also great periodic table and element games on-line here.

A refresher about atoms, elements and matter is hosted at Also provided for an advanced student are sections on math and chemical reactions. "Project Primary" at has K-3 activities on polymers, kitchen chemistry, and liquid nitrogen ice cream. A great site for minerals, soils, and clays can be found at Numerous links are summarized as well as downloadable activities. Wonderful kid sites that contain a lot of elementary science information, including some on chemistry, are Bill Nye's (, Beakman & Jax ( and Marshall Brain's (, see the Chemistry link).

May, 2001

A Medical Membrane Mimic

Kids, have you ever heard of kidney dialysis? Kidneys are essential for keeping the proper chemical balance in our blood. They perform a wonderful balancing act of filtration and osmosis that is not only essential to life, but is extremely complicated. In very simple terms, the kidneys filter blood in order to pass some dissolved salts, any toxins, urea, and creatinine, along with a little water. When the body digests proteins, urea is formed. But if too many urea molecules build up due to faulty kidneys, they can cause serious diseases. So, doctors and chemists have worked together over the years to perfect a process called hemodialysis. Chemists have especially helped in creating the special artificial membranes now used (hollow polysulfone fibers), which filter out urea but leave all the other beneficial molecules behind (like red and white blood cells and essential nutrients).

This is all hard to imagine, so here we describe an experiment testing a simple membrane model. In dialysis, small molecules pass through a membrane by diffusion. Itıs like dust blowing through a screen window while keeping bugs out. Diffusion also predicts which direction the molecules will move, which is from more concentrated to more dilute areas. Here a plastic bag will be the membrane. Iodine, starch, and water are the molecules. Starch and iodine combine to make a dark blue product and this will be the visual test of your model.

Make a thick cornstarch mixture of 1 tsp (3 gm) cornstarch in 1/8 cup (20 ml) water. Put 3/4 cup (180 ml) hot water in a thick clear glass (like a clear coffee mug or a 250 ml beaker). Slowly stir in the cornstarch slurry. Have an adult partner put just under 3/4 cup (150 ml) water and 1 tsp (5 ml) tincture of iodine in another clear glass. Cut off the top (ziploc side) of a ziploc sandwich bag (not a freezer or storage bag). Pour about 1/4 cup of the cornstarch solution into the bag (cleanly!). Close the bag tightly with a twist tie. Gently set the bag in the iodine solution without letting the twisted top get wet. Observe every 3 min for 15 min. Check for color changes. Iodine molecules in the solution (orange) will flow by diffusion through the pores in the bag to the inside, where there is no iodine yet (flow is from concentrated to dilute). When iodine bumps into cornstarch molecules, they react to make the dark blue complex. Which molecules were able to travel through the pores of the bag, and which were not? What does this tell you about the size of the molecules, the size of the pores, and whether this is a good model of kidney dialysis?

Reference: David Thielk, ChemMatters, ACS, April 2001
Patient Handbook, the Kidney Transplant/Dialysis Assn.
For extra info, check out and

June, 2001

A Magnesium Marvel

Kids, have you ever wondered how those trick birthday candles work ­ the ones that keep re-lighting themselves after they are blown out? All you need for this monthıs experiment is a regular birthday candle, a "trick" birthday candle, matches, and an adult partner to light the candles for you.

To understand trick candles, you need to first understand how normal candles work. The key difference lies in the moment after the candle is blown out. In a normal candle, a smoldering ember in the wick causes a ribbon of paraffin wax smoke to rise from the wick. While the ember is plenty hot enough to vaporize paraffin, it is not hot enough to ignite the paraffin vapors coming off.

The key to a trick candle, then, is to add something to the wick that the ember is hot enough to ignite. After this material is ignited, the wick becomes hot enough to light the paraffin vapors. The most common wick additive is a metal called magnesium. Magnesium happens to burn (which means to combine with oxygen to make light and heat) really quickly at a fairly low temperature (low for fires anyway, at 800oF/430oC). Aluminum and iron metals both burn pretty well too, but they need higher temperatures.

Inside a burning wick, magnesium is shielded from oxygen and cooled by melted paraffin. But once the flame goes out, the ember ignites magnesium dust. If you watch the ember closely (and carefully!) youıll see tiny flecks of magnesium flicking off. Just one of these is needed to provide the heat that can re-light the paraffin vapors, and the candle flame comes back to life. You wonıt see this happening to the wick of a normal birthday candle. Check out these interesting weblinks for more information: describes how regular candles work, and has the original 1983 Japanese patent on trick candles.

Reference: Marshall Brainıs "How Stuff Works" website (with video) at

August, 2001

Proteins and Hard Boiled Eggs

Kids, did you ever wonder why eggs get hard when you boil them? It’s because they have lots of protein, especially in the egg whites. Here’s how it works. Protein is a polymer chain of amino acids that is flexible enough to fold up on itself in different ways based on their chemistry. It’s all wound up like a loose ball of string and held in place by weak bonds that are fairly easy to break apart. When that happens, the protein is called “denatured”.

Have an adult help you to hard boil an egg. Imagine what’s going on inside the shell. When heated, the protein molecules gain enough energy to shake apart the weak bonds and the proteins begin to unfold. With time and more heat, new and stronger bonds are formed between different protein molecules. Another way to break the weak bonds is through chemical action. If you put a raw egg white in vinegar, the acetic acid will break some bonds in the egg. Use a dark bowl to help see it better. The egg white will start to set right away and get sort of pickled. When using an alcohol like vodka instead, the ethanol will break the weakest bonds in the protein. A lot of alcohol is needed, so really cover up the egg white. You should see some white strands form, but don’t be tempted to stir for this will just make a mess. You can see the greatest effect when both the alcohol and vinegar are used together. Notice the differences between these three different solutions and their effects on proteins. Mechanical energy will also work; whisking egg whites will unfold proteins and cause new bonds to form, and it stays in a new low-density “fluffier” state. A cooked, chemically-altered, or well-beaten egg white will never to go back to its original wet and gooey state.

The yolk of the egg holds up better to both the mechanical energy and to the alcohol or vinegar attack. While there is a lot of protein in the yolk, there is also a lot of fat and other molecules that make it more difficult to denature. When hard-boiling eggs the recipe always calls for using a moderate heating process. High heat causes the proteins to get really tough and rubbery, and a chemical reaction between the yolk and the white leaves a green film around the yolk. Did you ever see this, maybe in an Easter egg? That film is actually iron sulfide, made from iron in the yolk and hydrogen sulfide from the white. It doesn’t hurt you of course and has no taste, but it doesn’t look too appetizing!

Next check out these websites: www.hows gives the scientific reason for the answer to the question of which came first, the chicken or the egg, and www.howstuffwork describes how a chicken makes an egg using some really cool inorganic chemistry.

Reference : Marshall Brain’s “How Stuff Works” website at /question616

October, 2001

An Elementary Game

Kids, did you ever think about building your own collection of chemical elements? This can be a fun science project and a great "Show & Tell" classroom session. Look back at our previous article on the periodic table (June 1998) and also at for great sites that discuss the more than 100 pure elements that exist in the universe. These sites will tell you the differences between elements, compounds (two or more elements bound together), and mixtures (two or more compounds).

Many of the elements are difficult to find in their pure state, but quite a few are fairly easy to get a hold of. A list of suggestions along with possible sources is provided below. How many of these elements can you find? Can you find any others on the periodic table that we haven't thought of here?

There are others that are a bit hazardous and so you should only let an adult partner handle them for you. Examples are mercury if kept contained in a thermometer or thermostat switch, and tungsten filaments if left in unbroken light bulbs.

References: T. D. Burns, Chemistry Activity Book, 1995, Woodkrafter Kits, Inc., Yarmouth, ME 04096-0808.

November, 2001

Chemistry & Art - Frescoes

Kids, a fun event called National Chemistry Week will take place this year Nov. 4-10, 2001. Check other articles in the Bulletin and the Chicago Section
web page for details in the Chicago area. The theme this year is "Celebrating Chemistry & Art". One of the related activities suggested on the American Chemical Society's website will be highlighted here.

Fresco means "fresh" in Italian. Paintings done on wet plaster are called frescoes because the plaster is fresh; this means that the plaster is still wet when the artist paints on it. One of the most famous frescoes ever painted took four years and was finished in 1512 by Michelangelo. It was painted 70 feet above the ground on the ceiling of the Sistine Chapel in Rome, Italy. Here we'll learn the technique that Michelangelo and his helpers used to make this work of art.

The materials you will need are: a small disposable plastic dessert plate and plastic cup, a "craft stick" (popsicle stick), plaster of Paris, water, acrylic paints or poster paints, and a paintbrush. The procedure is to put 2 tablespoons (T) of plaster of Paris in a small cup, add 1 T of water, and stir with the craft stick until the mixture is smooth. Pour the wet plaster onto the plastic plate. Smooth the plaster out with the craft stick until it covers the bottom of the plate. Dip the brush into one color of paint and paint the plaster right away. Before the brush is dipped into the paint a second time, rinse the paintbrush well in a cup of rinsewater. (If the brush is not rinsed before being dipped into the paint each time, plaster will get into the paint).

Is painting on plaster different than painting on paper? Experiment with the interesting designs that can be made as the paint and paintbrush are dragged through wet plaster. What happens to the surface of the plaster as it begins to harden? Does it become more difficult to paint? When the fresco is completely dry, twist the plate gently. This will loosen the fresco so that it comes out easily.

So, what is the chemistry here? As the fresco dries, a chemical in the wet plaster called calcium sulfate hydrate combines with water and hardens before all the water can evaporate. Therefore it doesn't shrink, and the fresco can last a very long time. If your fresco is kept safe it will last a long time, too.

As an additional activity, consider entering the 2001 poster contest called "Celebrating Chemistry: Then and Now". Judging categories are grades K-2, 3-5, 6-8, and 9-12. Call the ACS Office of Community Activities at 1-800-227-5558, ext. 6097 for details.

References: Go to the website for general details, and to the "activities and articles" section for this activity. We also used for this column.

December, 2001

Christmas Chemistry

Kids, did you ever think of the Christmas tree as a chemical kind of plant? The wood of most any tree can be separated into two major components. They can be thought of as the "hard" and "soft" parts, which are the fiber (hard) parts and the oils and other soluble parts (soft). The hard or structural part of wood has very long molecules called polymers. They are cellulose (almost half of the wood is cellulose!) and lignin. Cellulose is the major ingredient in paper. The soluble parts of wood are extracted and separated using methods that chemists have developed. Think of the colors and flavors that are "extracted" from a steeping tea bag. Extracted oils from a spruce tree give turpentine, pine oil, and resins. There's only a tiny amount of pine oil (or alpha-terpineol), but it gives a pine tree it's distinctive Christmas smell.

Now for snowflakes. It all starts with a tiny particle of soil, ash, or dust in a cold cloud. Around this a hexagonal (six-sided) ice plate forms. A hexagon is the favorite shape of water molecules in an ice crystal lattice. The corners that stick out are better at catching other water molecules than the edges. Because the growing ice crystal is tumbling in the cloud, and sees different temperatures and saturation levels, an infinite variety of growing snowflake patterns are possible. Hence, no two snowflakes are alike!

Finally, here's a silly song, sung to the tune of "Rudolph the Red-Nosed Reindeer". (Yes, chemists know that pure iron is a silvery metal, but when it rusts you get a red iron oxide).

Iron the Red-Tinged Atom

There was Cobalt and Argone and Carbon and Fluorine
Silver and Boron and Neon and Bromine
But do you recall the most famous element of all?

Iron the red-tinged atom
Has a very shiny orbital
And if you ever saw him
You'd enjoy his magnetic glow

All of the other molecules
Used to laugh and call him Ferrum
They never let poor Iron
Join in any reaction games.

Then one inert Chemistry eve
Santa came to say
Iron with your orbital so bright
Won't you catalyze the reaction tonight?

Then how the atoms reacted
And combined in twos and threes
Iron the red-tinged atom
You'll go down in Chemistry!

References: for "Swedish Christmas Chemistry" and for many "Chemistry Christmas Carols".

Updated 1/5/07