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.