PSLE
The graph shows the temperature of water in a pot from 1800 to 18 30.
- For how many minutes was the temperature of the water 55°C and below? Give your answer in min.
- During which two 5-minute intervals did the temperature of water decrease at the same rate? Give your answer in the following format. (Eg 01 00 to 01 15, 01 25 to 01 30)
- What was the change in temperature per minute from 1825 to 1830? Give your answer in °C/min.
(a)
Temperature of water that reached 55°C at 18 10.
From 18 10 to 18 30: 20 min
Duration that the temperature of water that reached 55°C and below = 20 min
(b)
Decrease in temperature of water
From 18 00 to 18 05: 79°C - 62°C = 17°C
From 18 5 to 18 10: 62°C - 55°C = 7°C
From 18 10 to 18 15: 55°C - 50°C = 5°C
From 18 15 to 18 20: 50°C - 34°C =
16°C
From 18 20 to 18 25: 34°C - 26°C = 8°C
From 18 25 to 18 30: 26°C - 10°C =
16°C
Two 5-minute intervals that the temperature of water decreas
es at the same rate are 18 15 to 18 20 and 18 25 to 18 20. (c)
Change in temperature per minute from 18 25 to 18 30
= 7 ÷ 5
= 1.4°C/min
Answer(s): (a) 20 min; (b) 18 15 to 18 20, 18 15 to 18 20; (c) 1.4°C/min