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Drop a piece of baker's yeast into a small bottle, add water, then shake the bottle. Insert a piece of glass tubing through a one-hole rubber stopper and seal the bottle with the stopper so that the tubing does not touch the mixture.
Pour some limewater into a second small bottle.
Insert two pieces of glass tubing into a two-hole rubber stopper and seal the bottle with it.
One piece of tubing should be long enough so it will be in the limewater, and the other should not touch the limewater. Connect a piece of rubber tubing from the first bottle to the longer tube of the second bottle.
Now set up a second set of two bottles in the same way, but place moldy bread or another type of fungus (e.g., mushrooms) in place of the yeast mixture in the first bottle.
Now set up a third set for control purposes by putting only molasses and water in the first bottle.
After 24 hours, you will find that nothing has happened in the control bottle; thus, the yeast or moldy bread must be responsible for making the limewater cloudy.
Cloudy limewater indicates that carbon dioxide is being given off by the mixtures.
Yeasts and molds are non-green plants, and, since they cannot manufacture their own food, they must live on other food sources. [Ask your brilliant teacher what it means for a plant to manufacture its' own food. I somehow don't think it is like growing an arm and then eating it.]
As an alternative experience, place a solution of yeast and water in small amounts in the bottoms of some soda pop bottles.
Add a few
drops of syrup to one bottle; add flour, gelatin, or grape juice to others.
Firmly attach a balloon to each bottle, and observe what happens. You
can see which
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