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DETECTING THE PRESENCE OF CARBON DIOXIDE
Oh, now! This is marvelous! In #Making Carbon Dioxide"we learned how to make carbon dioxide. In # Collecting Carbon Dioxide", we learned how to collect it after having made it. This section of Super Science NOW chooses to teach us how to tell when carbon dioxide is present!!! Oh well, there is no accounting for the timing used by brilliant scientists!
Here goes--this tells us several tests we can perform to detect the presence of carbon dioxide.
How much do you want to bet that the brilliant scientist fails to teach us to read the list of ingredients on the labels of the stuff we buy?
a. Collect some carbon dioxide in a test tube and place a thumb over the tube, making sure that the test tube is upright. Carefully pour a small amount of clear lime- water into the tube, and observe what happens. (The lime-water will turn milky, indicating the presence of carbon dioxide.)
To show that carbon dioxide is present in air, place a few spoonfuls of clear lime-water in an open container for several days. Note that white deposits of lime- stone form around the edge of the container at the surface of the lime-water. (This is the result of carbon dioxide in the air combining with the lime-water.)
To see that your own breath contains carbon dioxide, exhale through a straw into a glass of clear lime- water. You will find that it takes a great deal of blowing to turn the liquid milky. (Exhaled breath contains very little carbon dioxide -- about 3 to 4 percent.)
You can also invert a jar over a burning candle or germinating seeds, then test the candle and seed "airs" to see if they contain carbon dioxide.
b. Collect carbon dioxide by letting dry ice set in a wide-mouthed container for several minutes. A glowing splint or lighted wooden match placed in the container will go out because carbon dioxide does not support combustion and can keep air away from a fire. Do you see? We were not told to read the labels!
It is interesting to see that only 3 or 4 % of what we exhale is carbon dioxide. I always thought that all of our used breath was carbon dioxide. That is one of the reasons that I am a writer instead of a brilliant scientist!
This project tells us that carbon dioxide "does not support combustion and can keep air away from a fire." I wonder if carbon dioxide is one of the ingredients in fire extinguisher chemicals?
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