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Diagrams, charts and graphs
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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/mins05101520253035404550
Temperature/°C9065605036353026252220
  • (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.