Diagrams, charts and graphs

# 2.1.1 Try some yourself

## Activity 6

The table below indicates the cooling rate of tea in a teapot.

##

Time/mins | 0 | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50
Temperature/°C | 90 | 65 | 60 | 50 | 36 | 35 | 30 | 26 | 25 | 22 | 20

- (a) How long does it take for the tea to cool to 50°C?

- (b) By how much does the temperature drop in the first 20 minutes? By how much does it drop in the second 20 minutes?

- (c) How would you describe the pattern of cooling?

## Answer

- (a) 15 minutes.

- (b) The temperature drops from 90°C to 36°C in the first 20 minutes, a total of 54 degrees. In the second 20 minutes, the temperature drops from 36°C to 25°C, a total of 11 degrees.

- (c) The tea cools quickly at the beginning when it is hot, then cools more slowly when it is cooler.

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