Cambridge Secondary (7-9). Stage 9. MCE Science. Workbook - Unit 8: Rate of Reaction - Question 18

In this experiment, add 50 ml of dilute hydrogen peroxide (1.5 M) to a conical flask, then add 1 g of yeast. Quickly fit a stopper connected by a delivery tube to an inverted, water-filled measuring cylinder in a water trough. Collect oxygen over water and record its volume every 30 seconds. Wear safety goggles and gloves.

Explain why the rate of reaction changed over time.