Calculating Heat Change for Freezing Water

Understanding Heat Change for Freezing Water

Heat of Fusion: The heat of fusion of a substance is the amount of energy required to change one gram of a solid into a liquid at its melting point without changing its temperature. For water, the heat of fusion is 79.8 calories per gram.

When calculating the heat change for freezing water, you need to consider the amount of water (40g in this case) and the heat of fusion of water. By multiplying the mass of water by the heat of fusion, you can determine the heat change during the phase transition from liquid to solid.

In this scenario, multiplying the mass of 40g by the heat of fusion (79.8 cal/g) gives us: 79.8 cal/g * 40 g = 3192 cal. Rounding to two significant figures, the heat change is expressed as 3200 calories.

It is important to note that the heat change value is positive, indicating that energy is absorbed during the process of freezing water at 0°C.