The cardboard volcano is a dramatic way of demonstrating chemical reactions. When vinegar and baking soda combine together, they rapidly release carbon dioxide gas, causing the liquid to bubble up violently. This reaction is dramatic enough on its own, but when it occurs inside a cardboard volcano, it can really make you blow your top!
Cut out a circle of cardboard. It should be as wide as you want the base of your volcano to be.
Glue a bottle in the middle of the cardboard circle. A bottle with a narrow opening such as a soda bottle will make the lava shoot out more violently, whereas a bottle with a wider opening will just ooze lava out.
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Cut several strips of cardboard and tape or glue them between the sides of the bottle and the base. Use the strips to make the approximate shape of your volcano. Be sure to leave the mouth of the bottle open.
Mix 3 parts water and 1 part white glue in a bowl. This is your paper mache mix.
Rip a 2-inch wide strip of newspaper. Dip it in the bowl to wet it, then wring water out of it, then paste it onto the side of the volcano. Keep ripping off strips and pasting them on until you have built a cone for your volcano. Do not cover up the mouth of the bottle.
Let the volcano dry. The volcano can take anywhere from overnight to several days to dry, depending on how large and how wet it is. You can speed up the process by taking a hair dryer and blowing hot air on it. Once it is dry, paint the volcano.
Pour 3/4 of a cup of distilled vinegar into the mouth of the bottle. Add several drops of red food coloring.
Add a squirt of soap into the bottle. The actual amount isn't that important, since the soap just adds bubbles to the reaction.
Put about 3 tbsp. of baking soda into a cup. When you are ready for the volcano to go off, pour the baking soda into the bottle. Red "lava" will bubble up and out of the volcano.
If you don't add soap, you will get a faster reaction with no bubbles. It will go off like a rocket instead of like a volcano flowing with lava.