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# 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.

MU120_4M5

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