Question 40
FA student investigates how the number of layers of insulation around a beaker affects how quickly hot water in the beaker cools.
The Figure shows the side view of the apparatus.
Figure
This is the student's method.
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pour 200 cm3 of water at 80 ∘C80\ ^{\circ}\text{C}80 ∘C into the beaker
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record the temperature of the water after 10 minutes
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repeat with a different number of layers of insulation
The Table shows the results.
Table
| Number of layers of insulation | Temperature after 10 minutes in ∘C^{\circ}\text{C}∘C |
|---|---|
| 0 | 56 |
| 1 | 62 |
| 2 | 66 |
| 3 | 68 |
| 4 | 69 |
a.[2]
Give two variables the student should keep the same in each test.
b.[2]
Describe the relationship between the number of layers of insulation and the temperature after 10 minutes.
c.[2]
Explain, in terms of energy transfer, why the water with more layers of insulation cools more slowly.
d.[2]
Explain why the student should use the lid in every test.