This document provides instructions for demonstrating how yeast converts sugars into carbon dioxide and ethanol through a simple experiment. The experiment involves adding yeast, sugar, and warm water to a bottle or test tube, sealing it with a balloon, and observing the balloon inflate over 30 minutes as the yeast produces carbon dioxide from fermenting the sugar. Testing the gas in the balloon with lime water confirms it is carbon dioxide produced by the yeast during alcoholic fermentation.

1. 065 FERMENTATION (ALCOHOLIC)
To demonstrate how yeast converts sugars into carbon dioxide and ethanol
MATERIALS REQUIRED
One empty bottle / test tube
One tumbler warm water
One packet active dried yeast
4 tablespoons sugar
One rubber balloon
Freshly prepared lime water
warm water
bottle
rubber balloon
yeast sugar

2. First fill the bottle / test tube with warm water. Add yeast to it and
shake the bottle / test tubes a few times to mix the yeast with water.
Add the sugar and shake for some more time.
Blow the balloon up slightly and place over the neck of the bottle / test
tube with gentle care. Let the bottle/test tube sit for about 30 minutes.
In due course of time the balloon will inflate.

3. Carefully remove the expanded balloon from the bottle / test tube
with great care so as not to release the carbon dioxide;
Release the gas trapped in the balloon into a test tube containing
fresh lime water;
If the lime water turns milky it is confirmed that the gas in the balloon
is carbon dioxide
lime water
turns milky

4. As the yeast consumes the sugar, it produces carbon dioxide. The gas
initially fills the bottle/test tube and with no place to go but up, this gas
slowly fills the balloon thereby expanding it.
The same mechanism occurs while baking bread. The yeast releases the
carbon dioxide gas which expands and makes many small holes in the
bread. This makes the bread light and fluffy. Baker’s yeast is
Saccharomyces cerevisiae