A sample of water weighing 125g releases 10.0 kcal of heat as it cools from 80.5ºC to 0ºC. It then releases another 10.0 kcal of heat as it freezes at this temperature. How many kcal of heat are needed in order to convert 125g of ice at 0º to water at 80.5ºC?
We know that heat released or absorbed is given by q = m C dT, where m is the mass C is the specific heat and dT is the change in temperature.
Heat is released when water at 80.5 deg C cools to 0 deg C. This value is q1 = 10 kCal. The amount of heat required per unit mass of a substance at freezing point (constant), and under 1 atmosphere pressure to convert it from the liquid to the solid state, is called Latent Heat of Freezing.
q = m ...
The solution outlines the conversion between ice and water, with heat as the prime factor. With the parameters established, the specific amount of kcal of heats are stated as the amount needed to convert ice to water.