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Carbon dioxide is a by-product of burning, like a candle, and can also come from some kinds of chemical reactions like baking soda and vinegar. Are there any other sources of carbon dioxide in the atmosphere? This experiment will provide some evidence of another source.
Material Required
• Cabbage
• Small water glasses
• Straw
• Carbon dioxide generator from the previous exploration
Procedure
This exploration requires keen observations of color change. You may want to take before and after pictures of the color changes to help you remember what you saw!
1. Find a purple cabbage.
2. Chop some into tiny pieces
3. Place the cabbage pieces in a bowl of warm water and stir. Pour the mixture through a strainer.
4. You should have a small amount of cabbage water.
5. Pour clean water into a glass so it is about 1/3 full
6. Using a straw, put it into the cabbage juice and put your finger on the other end. Then place the straw and juice over the clean water and release your finger. Do this twice so that the water turns a light blue.
7. Prepare the carbon dioxide generator as used in the previous experiment.
This apparatus consists of a water bottle with a hole just large enough for a straw, vinegar in the bottom of the bottle, and a ball of baking soda. and a straw that can reach into a liquid below.
8. Prepare the apparatus and allow the baking soda and vinegar to mix. Then the CO2 bubbles through the blue cabbage juice.
9. After a time of bubbling C02 in the blue liquid. Note the color of the cabbage juice. The color change is a response to some of the carbon dioxide mixing with the water and making a weak acid. When cabbage juice comes in contact with acid, it changes to purple and then to red.
Now that we have a way to test for CO2, let's see if we can check for other sources of where CO2 is made.
10. Prepare a glass of water and two "straws" of cabbage juice as before.
11. Using a straw, blow into the blue water. This is your exhaled air. This may take a few minutes!
12. What happens to the color of the blue water?
Questions
Based on your observations, what must your breath contain?
Based on how long it took to change, how much CO2 do you exhale?
Discussion
It may not seem obvious at first, but humans, as well as all other animals, use oxygen, "burn" sugar, and the byproduct is water and carbon dioxide. Review how carbon moves in plants and animals by watching this video:
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