12.5 Investigation: Temperature & Respiration
Paper 6: Alternative to Practical
Research Question: How does temperature affect the rate of respiration in yeast?
Apparatus & Method
Equipment Required:
- Water bath with temperature control
- Test tube containing yeast suspension
- Glucose solution
- Delivery tube
- Beaker of water (inverted measuring cylinder)
- Thermometer
- Stopwatch
Safety Notes:
- • Wear safety goggles when handling hot water
- • Do not exceed 80°C (risk of boiling)
- • Handle glassware carefully
Variables:
Independent Variable:
Temperature of water bath (10°C - 80°C)
Dependent Variable:
Volume of CO₂ produced (or rate of bubbles per minute)
Control Variables:
- • Concentration of glucose solution
- • Mass/volume of yeast suspension
- • Time period for measurement
Method:
- 1.Set up water bath at desired temperature
- 2.Add glucose solution to yeast suspension in test tube
- 3.Insert delivery tube through bung into test tube
- 4.Place other end of delivery tube into inverted measuring cylinder
- 5.Allow apparatus to equilibrate for 2 minutes
- 6.Count bubbles of CO₂ produced per minute
- 7.Repeat at different temperatures (10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C)
- 8.Plot results on a graph
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