Have you ever wondered why some things fizz, bubble, foam, or change shapes or colors when you mix them together? Here you will learn the science behind some very cool reactions – and you can even try them out at home!

Crazy Chemistry Projects

Up, Up, and Away!

Well, your balloon might not quite fly away in this experiment, but you can make it inflate by creating a reaction in a bottle.

What You Need:

  • 1 packet (or 2 teaspoons) of active dry yeast
  • 1 tablespoon of sugar
  • 1 cup of warm water
  • A clean, empty plastic bottle (the kind soda or water comes in)
  • A sheet of paper
  • A balloon
  • Notebook
  • Pencil

What You Do:

  1. Stretch the balloon out by blowing it up and releasing the air three times.
  2. Pour the warm water into the bottle. Make a funnel by rolling a piece of paper into a cone shape, then put the pointed end into the mouth of the bottle. Pour the sugar into the bottle through your funnel. Put the cap on and shake the bottle until most of the sugar has dissolved. Take the cap off.
  3. Put your funnel in the mouth of the bottle and pour the yeast in so that it floats on top of the sugar water.
  4. Quickly attach the balloon to the mouth of the bottle.
  5. Set the bottle in a place where it won’t be disturbed and write in your notebook what time it is.
  6. Go back and check the bottle after two minutes and write down changes you see to the liquid in the bottle or to the balloon.
  7. Check it again in five minutes and write down any changes. If it doesn’t look like much is happening, leave it for about 15 minutes and then look at it again.
  8. Continue to check on the bottle and balloon about every 15 minutes. The reaction may continue for up to several hours. Watch closely and write down any changes you notice!

What Happened:

Yeast bubblingThe warm water made the yeast ‘wake up’ and it immediately started to have a chemical reaction with the sugar. Two substances, yeast and sugar, reacted to each other and together they made a new substance – a gas called carbon dioxide. Carbon dioxide is the same gas that makes soda pop fizzy, and one of the many gases in the air we breathe in and out. The carbon dioxide from the reaction filled up all the space in the plastic bottle and kept rising to fill up the balloon. At first, the yeast should have looked puffy or bubbly on the surface of the water as it was beginning to react with the warmth of the water. Then, you probably noticed that the balloon was standing straight up instead of being flopped over the mouth of the bottle! That was the first sign that the yeast was reacting with the sugar and that carbon dioxide gas was being made. Soon after that, the balloon should have started to inflate. Since the balloon was made of stretchy rubber (and you helped stretch it out), it kept expanding to hold the carbon dioxide, the same as it would if you were to blow it up with your mouth. When you breathe out (or exhale), your lungs push carbon dioxide out, along with a few other gases, which is how you are able to blow up a balloon.

Now that you know how it works, you might want to try the experiment with other types of sugar mixtures. What do you think would happen if you used your favorite soda or juice instead of the sugar water?

So, if yeast and sugar react this way in a bottle, what happens when you bake with them? Well, the same thing happens, it just looks a little different. Bread and many other baked goods are made from yeast. The yeast reacts with the sugar in the dough and releases carbon dioxide, which creates tiny air bubbles that pop and leave air pockets as the dough bakes into bread. You can get a closer look at the air pockets left behind in a slice of bread.

Slime Time

What You Need:

  • White glue
  • Water
  • Food coloring
  • Borax powder
  • Glass or ceramic bowl
  • Small mixing bowl or cup
  • Measuring cup
  • Measuring spoon
  • Mixing spoon or popsicle stick
  • A square of chocolate

What You Do:

  1. Measure 1 cup of water into the small bowl or cup and add the Borax powder. Stir it well and set it aside. You just made a solution of Borax.
  2. Rinse your stirring spoon to get all of the Borax solution off of it.
  3. In the larger bowl, measure 1/2 a cup of water and 1/2 a cup of white glue. Stir it well until it is all mixed together.
  4. If you want colored slime, add 2-3 drops of food coloring to the glue mixture now.
  5. Pour the Borax solution that you made in step one into the glue mixture and start stirring. You should see a big clump form in the colored glue right away, just keep stirring though until the clump has picked up as much of the liquid around it as it can.
  6. Now comes the fun part – set your spoon aside and pick up the slime with your hands. Keep it over the bowl and knead it like dough, working it between your fingers. As you play with it, the slime will dry off on your hands and will become less slimy and more like putty.
  7. Keep your slime in a plastic zip-lock bag in the fridge when you are not playing with it.

What Happened:

Kids having fun with slimeThe slime you just made is called a polymer (say: PAUL-UH-MER). The word polymer means ‘many parts.’ White glue is one type of polymer. When you mixed water with the white glue, the glue formed long chains of thousands of little molecules that you couldn’t see until you added the Borax solution. The Borax had a reaction with the glue – it linked all those chains together, which made the whole mixture thicker and turned it into a blob of slime, a different type of polymer!

There are lots different types of polymers, including plastic, rubber, Jell-O, glue, camera film, materials such as nylon, and even natural fibers from wood and cotton. This polymer has properties of a solid and a liquid at once. Compare your polymer to a solid object – a piece of chocolate. Break the chocolate in half. Try quickly breaking the wad of slime in half. Did you get a clean break similar to the way the chocolate broke? To see how it is also like a liquid, try slowly stretching the blob out between your hands. You can’t do that with a solid piece of chocolate! The polymer is showing its liquid properties when you stretch it slowly. Now set the slime back into the bowl you made it in and watch what happens. It should flatten out to fill the bottom of the bowl, similar to a liquid like pancake batter would do.

Slime Science Lesson

Chemical Reactions

There are all sorts of reactions going on around us each day. A chemical reaction is something that happens when two or more substances come into contact with each other. One substance combines with another and creates a whole ew substance that wasn’t there when the reaction started. Different types of reactions can happen depending on the substances that are put together. Sometimes a little of the original ingredients will be left over after the reaction, and sometimes more than one new substance will be formed in the reaction. In Up, Up, and Away! the yeast reacted with the warm sugar-water and produced carbon dioxide, which you could see filling up the balloon.

Boy eating a sandwichThere are also many other types of chemical reactions that take place around us and even inside of us every day! Can you think of any examples? Here are a few to get you started:

  • Digestion – whenever you eat, your body uses many different and very complex chemical reactions to break down the food and convert it into energy and other things that your body needs! (You can learn more about digestion on this page.)
  • Combustion – fire is another type of chemical reaction, called combustion. It needs oxygen, fuel, and heat in order to exist and the reaction creates light, heat, and smoke.
  • Oxidation – rust is a chemical reaction that you might see happening somewhere around you. Sometimes a reddish-colored layer will form on iron or steel (types of metal) when the metal reacts with oxygen in the air. Most iron and steel is treated to prevent it from rusting, though, so you usually only find rust on old pieces of metal that have been in contact with a lot of water and have gradually rusted over several years. When an apple turns brown after you bite into it, that is oxidation, too. An enzyme in the flesh part of the apple reacts with oxygen from the air and turns the apple brown.


Pile of tires

In the slime experiment above, you learned what a polymer is – a long chain of hundreds or thousands of tiny molecules. The slime you made is an interesting type of polymer that can act like a solid or a liquid depending on how it is handled. There are lots and lots of polymers in our world. Some are natural and some are made by humans, or synthetic. Here are a few examples of polymers:

  • Plastic is one of the most common polymers. There are lots of different types of plastics that have very different properties – some plastics are flexible and can be bent (like a plastic bag or a toothpaste tube) and some are very solid and would split or crack if you tried to bend them (like a plastic plate or a CD).
  • Fabric such as rayon, nylon, and polyester that are used for making clothes such as shirts, sweaters, and socks.
  • Natural polymers – one of the most important natural polymers is DNA, the protein in your cells that makes you who you are! Some other things that come from naturally-occurring polymers are cotton, silk, rubber, paper, and leather. Rubber comes from a natural source – a plant! Before it can be used though, it has to be processed.

For more information and project ideas for teaching kids about polymers, check out our Polymer and Slime Experiments page.

Science Words

Chemical reaction– when two or more substances come into contact and form a new substance.

Carbon Dioxide– a gas that is in the air on earth, but in very small amounts. Plants need it in order to live; they use it to covert sunlight into food. Humans breathe out carbon dioxide when we exhale. In chemistry, it is abbreviated CO2, which means that is has one carbon atom and two oxygen atoms.

Oxygen – a gas that is very abundant on earth and that humans and most animals breathe to stay alive. It does not have any color, smell, or taste.

Polymer– the word “poly” means many, so a polymer is a long chain of molecules that gives a substance the ability to stretch and be very flexible.

Printable Worksheet

Use this worksheet as a fun activity to reinforce the basic chemistry concepts of chemical reactions and polymers. Kids can color the page and then determine whether each picture is a polymer, a reaction, or neither.