First, we'll need to know the latent heat of fusion for ice. Typical value (may be found in texts or handbooks) for the latent heat of freezing for water is 80 cal/g.

The formula used to solve this is Q = mL_{f}, where L_{f} is called the " latent heat of fusion." L_{f} is measured for different substances at their melting/freezing points or temperatures.

Thus, **Q = 1000g x 80.0cal/g = 80,000cal of heat or 80.0kcal** of heat removed.

In this problem, the heat calculation involves a phase change only. There is no temperature change.

Energy is required to melt a solid because the cohesive bonds between the molecules in the solid must be broken apart such that, in the liquid, the molecules can move around at comparable kinetic energies; thus, there is no rise in temperature. Similarly, energy is needed to vaporize a liquid, because molecules in a liquid interact with each other via attractive forces. There is no temperature change until a phase change is complete. The temperature of a cup of soda initially at 0ºC stays at 0ºC until all the ice has melted.

Conversely, energy is released during freezing and condensation, usually in the form of thermal energy. Work is done by cohesive forces when molecules are brought together. The corresponding energy must be given off (dissipated) to allow them to stay together.

The energy involved in a phase change depends on two major factors: the number and strength of bonds or force pairs. The number of bonds is proportional to the number of molecules and thus to the mass of the sample.

The strength of forces depends on the type of molecules. The heat Q required to change the phase of a sample of mass m is given by Q=mL_{f} (melting/freezing), Q=mL_{v} (vaporization/condensation), where the latent heat of fusion, L_{f}, and latent heat of vaporization, L_{v}, are material constants that are determined experimentally.

Learn more about phase change and latent heat at Philschatz.com and Pstcc.edu.