Question

how much heat is necessary to change 450g of ice at -11 degrees c to water at 20 degrees Celsius?

Answer 1

The heat Q required to change the temperature of a substance of mass m from T_i to T_f is

where C is the specific heat of the substance.

Consider the process in three steps:

1. Increase in temperature of ice from -11^oC to 0^oC.

2. Change in phase of ice (solid) to water (liquid) at 0^oC.

3. Increase in temperature of water (liquid) from 0^oC to 20^oC

The heat required in the first step is

where C_ice is the specific heat of the ice

The heat required in the second step is

where L_fusion is the latent heat of fusion of water.

The heat required in the third step is

Total heat required is

Substituting , , , we get