Question

100 g of ice at 0°C receives a steady flow of heat energy. At 0°C, the ice melts into the water in 1 minute. How long would it take to bring water from 0°C to 20°C?

[Given: specific heat capacity of water = 4.2 J g⁻¹°C⁻¹ and specific latent heat of ice = 336 J g⁻¹].

Answer 1

Given:

Mass of ice/water, m = 100 g

Latent heat of ice, L = 336 J g⁻¹

Specific heat capacity of water, c = 4.2 J g⁻¹°C⁻¹

Time taken to melt ice = 1 minute

1. Heat required to melt the ice:

Q₁ ​= mL

= 100 × 336

= 33600 J

So, the heat supplied per minute is 33,600 J/min.

2. Heat required to raise water from 0°C to 20°C:

Q_2​ = mcΔT

= 100 × 4.2 × 20

= 8400 J

3. Since the heat flow is steady,

t = `8400/33600 xx 1`

= 0.25 minute​

= 15 seconds