Are yeast living organisms?

Class: 5.

Lesson: Les levures

Rationale:

1. Demonstrate that yeast respires.
2. Use to demonstrate the scientific method.

Materials:

Procedure:

1. The water mixed with the yeast needs to be warmed to finish this experiment in 5 minutes instead of 2 hours. To take warm water to school, boil water before leaving for school. Pour into a jar and wrap the jar in a towel. The water will stay adequately warm for at least four hours.

2. Mount the two stands and clamps on the lid of the science kit.

3. In the metal test tube, add 1 tsp of yeast and 1 tsp of sugar. Fill the test tube halfway with warm water and mix

4. Insert the 3 in plastic tube in the stopper.

5. Close the tube with the holed stopper.

6. Mount the test tube in one clamp.

7. Fill the graduated cylinder with water. Invert it in a bowl of water and mount it in the second clamp.

8. Attach the hose to the test tube and insert the other end of the hose in the graduated cylinder.

Test tube

9. Almost immediately the gas will begin collecting in the graduated cylinder.

10. After the graduated cylinder is full of gas (>5 min), use a lighted match to show that the gas is carbon dioxide.

Source: HBJ Concepts in Science Orange, p. 232 with modifications by C. Huss.