Soda has something in it that almost no other liquid has: lots of carbon dioxide. This experiment explores what happens to raisins when carbon dioxide bubbles attach themselves to them.CAROLINE TOMPKINS/The New York Times News Service
Let’s Talk Science and the Royal Society of Canada have partnered to provide Globe and Mail readers with relevant coverage about issues that affect us all – from education to the impact of leading-edge scientific discoveries. Let’s Talk Science offers a number of fun activities to get youth engaged in STEM.
Let them bop ‘til they drop! What causes these raisins to reach new heights in this hands-on activity?
What You Need
● Clear carbonated soda (soda water) or clear carbonated soft drinks
● Water
● Glass/plastic containers (the taller the better) - 2
● Raisins
What to Do
- Fill 1 container with clear soda and 1 container with water.
- What do you think will happen when you add raisins to each container?
- Place some raisins in each container.
- Observe!
- Optional: Watch this short video (Dancing Raisins Experiment - 1:35 min.) demonstrating and explaining what is happening.
What’s happening?
Soda has something in it that almost no other liquid has: lots of carbon dioxide. The carbon dioxide in soda is a gas that makes it bubbly. There are some places in nature where water absorbs lots of carbon dioxide by flowing over rocks and minerals with certain chemicals in them. Soda has had carbon dioxide added to it.
When we put the raisins into the soda, the carbon dioxide molecules moving around the raisins slow down. As more carbon dioxide molecules hit the raisin, they begin to build up near the raisin and attach to it. The combination of raisin and carbon dioxide gas is less dense than the raisin alone, so when many “bubbles” form on the raisin, they lift the raisin to the surface. When some of the bubbles break, the density increases, the raisins sink and then the whole process is repeated. This makes the raisins appear to dance!
Why does it matter?
Pockets of air or gases within solid materials make many things (both natural and man-made) less dense. Air spaces in boats make a boat able to float on water. Life jackets are filled with spongy material with lots of air spaces that make the overall jacket less dense and more able to float on water and hold up a person. Sponge and pumice are natural materials that can float because they are less dense than water due to the millions of tiny air spaces they contain.
Carbon dioxide, created as a result of acid-base chemical reactions, is important in baking to make bubbles form in cakes or cookies as they are baking. This helps make cakes and cookies light and spongy, rather than heavy and dense.
Investigate further
● Repeat the experiment using different objects such as rice, dried kidney beans or paper clips.
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