Year 8 Science · Unit 3 · Lesson 9
Challenge Worksheet
Learning Goals
Design a mini-experiment
A scientist wants to test: "Does temperature affect the rate of yeast fermentation?" You will use CO₂ production (measured as bubbles per minute from a balloon placed over the flask) as the dependent variable. Plan the investigation fully in the table below.
| What I will change (independent variable) | |
| What I will keep the same (controlled variables — list at least 3) | |
| What I will measure (dependent variable) and how | |
| Temperatures I will test (suggest at least 4 specific values in °C) | |
| My prediction (include a reason using fermentation chemistry) | |
| How I would know if my prediction is wrong | |
| One limitation of this experiment and how to address it |
1. A student sets up the yeast experiment but uses hot water at 90°C. The balloon over the flask does not inflate at all. Suggest a scientific explanation for this unexpected result, using what you know about fermentation and enzymes.
2. CSIRO sports scientists study energy release in muscles during exercise. They know that at very high exercise intensity, muscles switch from aerobic respiration (using oxygen) to anaerobic fermentation (without oxygen). What gas is NOT produced during anaerobic fermentation in muscles? What product builds up instead, and what physical effect does this have on the athlete?
Wrap Up
In one sentence, what was the main idea of this lesson?