Question 20
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.
What result did you observe with mixture 1? Did you expect this result? Say why or why not.
What result did you observe with mixture 1? Did you expect this result? Say why or why not.
