Worked examples

Three examples from the textbook.

Example 1

heating 2 kg of water by 10 K (c = 4200 J kg^-1 K^-1)

Q = mcθ = 2 × 4200 × 10 J

Q = 84 000 J

Example 2

500 g of aluminium from 30 °C to 50 °C (c = 900 J kg^-1 °C^-1)

Q = mcθ = 0.5 × 900 × (50 − 30) J

Q = 9000 J

Example 3

20 000 J given to 2 kg of copper at 30 °C: its final temperature? (c = 400 J kg^-1 K^-1)

20 000 = 2 × 400 × θ

θ = 20 000 ÷ (2 × 400) = 25 °C

Final temperature = 30 °C + 25 °C = 55 °C