Saturday, June 26, 2010


PURPOSE : To observe the effect that yeast has on a sugar solution.

MATERIALS : 1Package of powdered yeast
                           Glass soda bottle
                           Measuring spoon – tablespoon (15 ml)
                           Measuring cup (250 ml)
                           10 inch (25 cm) balloon


  •  Mix the package of yeast and one spoon of sugar in one cup of warm water. Be sure the water is warm, not hot.
  •  Pour the solution into the soda bottle.
  •  Add another cup of warm water to the soda bottle.
  •  Squeeze the air out of the balloon and place it over the mouth of the bottle.
  •  Observe the bottle daily.

RESULTS : Bubbles are continuously being formed in the liquid. The balloon is partially inflated.

WHY ? Yeast is a fungus. It has no chlorophyll like other plants and cannot produce its own food. Like animals, yeast can use food such as sugar to produce energy. The yeast causes the sugar to change into alcohol, carbon dioxide gas, and energy. The bubbles observed in this experiment are carbon dioxide. This same gas causes bread to rise during backing as the bubbles push the moist dough up and out ward. Gas holes can be seen in the finished bread. The nice smell from the backing of yeast bread is partially due to the evaporation of the alcohol produced.

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