Question 16
Work in groups. Wear eye protection and gloves; handle yeast carefully and avoid contact with eyes, skin and clothing. Mix 5 g of active dry yeast with 30 cm³ of warm water (35–40 °C). Label two clear plastic bottles mixture 1 and mixture 2. Mixture 1: 100 cm³ water + 15 cm³ yeast mixture. Mixture 2: 10 g sugar + 100 cm³ water + 15 cm³ yeast mixture. Cap and shake each bottle, then remove the caps and fit a balloon over each opening (stretch its opening if needed). Start a timer. Yeast is unicellular and releases carbon dioxide during respiration. Respiration releases energy; it is not breathing.
Observe the solutions every 5 minutes for the next 20 minutes. Notice whether the balloons are inflating more or not. Record your observations from step 7 in the table below.
| Time in min | Inflation of balloon: Mixture 1 | Inflation of balloon: Mixture 2 |
|---|---|---|
|10| | |
|15| | |
|20| | |
|25| | |
|30| | |
Observe the solutions every 5 minutes for the next 20 minutes. Notice whether the balloons are inflating more or not. Record your observations from step 7 in the table below.
| Time in min | Inflation of balloon: Mixture 1 | Inflation of balloon: Mixture 2 |
|---|---|---|
|10| | |
|15| | |
|20| | |
|25| | |
|30| | |
