You and Your Students!
Vicki Cobb, Education World Science Editor
How can you speed up (and slow down) the way bananas ripen?
A banana is a living system that changes or ripens over time. The ripening process is accompanied by changes in color, texture, odor, and, of course, taste. Whenever easily observable changes occur, you can be sure you have a good subject for scientific investigation.
Begin the activity by asking your students how they can tell an unripe banana from a ripe one.
Those are the questions this activity will set out to answer.
Set up this activity as a class project; or students might work in small groups to carry it out.
Set up the bananas in their environments as follows:
Leave the fruit alone for four or five days to ripen. Do not open any of the bags during that period. On the fifth or sixth day, examine all the fruit.
Ripening fruit "breathes," or respires. That means that it takes up oxygen and gives off carbon dioxide. Oxygen is essential for the chemical reactions involved in ripening.
In addition, ripening fruit gives off another gas -- called ethylene. Not only is ethylene a product of ripening fruit, in some mysterious way it also stimulates the further ripening of the fruit. For that reason it has been called the "ripening hormone." (Hormones are chemicals produced by living things that stimulate cellular changes.)
Paper bags tend to keep in ethylene, but they are porous enough to allow oxygen (and ethylene) to pass through. As a result,
Now you can see why supermarkets sometimes sell bananas sealed in plastic.
How does this experiment explain how one rotten apple spoils the barrel?
Article By Vicki Cobb
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