This practical can be done as a demo or class experiment provided you have enough materials for the whole class.
Fermentation is the process of breaking down of food by micro-organisms using anaerobic respiration. Yeast is a single-celled fungus, and reproduces by growing buds out of the cell and feeds itself on sugars like glucose. In the process of fermentation, the yeast makes alcohol (Ethanol) and carbon dioxide. To illustrate it better, consider the equation below
The Equation:
GLUCOSE --> ETHANOL + CARBON DIOXIDE