Question

A burner is supplying heat at a rate of 50 J s⁻¹. A solid with a specific heat capacity of 720 J kg⁻¹ K⁻¹ is heated from 20°C to 100°C in one minute. Find the mass of the solid.

Answer 1

Given:

Rate of heat supply (P) = 50 J s⁻¹

Time (t) = 1 minute = 60 seconds

Specific heat capacity (c) = 720 J kg⁻¹ K⁻¹

Initial temperature (T₁) = 20°C

Final temperature (T₂) = 100°C

Rise in temperature (ΔT) = 100°C − 20°C = 80°C (or 80 K)

Heat supplied = Power × Time

= 50 × 60

= 3000 J

Using Q = mcΔT

3000 = m × 720 × 80

$$m = \frac{3000}{720 \times 80}$$

$$= \frac{3000}{57600}$$

= 0.052 kg

The mass of the solid is 0.052 kg (or 52.1 g).