Final answer:
The question deals with the heat of fusion and solidification, specifically the energy required to melt or freeze 1 kg of a substance, like water. One kilogram of ice requires 334 kJ to melt at 0°C, and the same amount of energy is released when water freezes. These values are vastly different from the energy required for simple temperature changes of the substance.
Step-by-step explanation:
The student's question pertains to the heat of fusion and heat of solidification of a substance, specifically regarding the energy involved in melting and freezing 1 kg of a substance. In the case of water, the latent heat of fusion is the heat required to convert ice to water without a change in temperature. For melting 1 kg of ice at 0°C, the energy required is 334 kJ (also represented as 3.34×105 J). Conversely, when 1 kg of water freezes, the same amount of energy is released back into the surroundings.
These processes are significant because they involve large amounts of heat transfer compared to heating the substance by raising its temperature. Heating 1 kg of water from 0°C to 79.8°C requires the same amount of energy as melting 1 kg of ice at 0°C. Additionally, the latent heat coefficient is a constant that indicates the amount of heat transfer per kilogram during a phase change of the substance.
The specific heat is another thermal property which defines the amount of heat energy needed to raise the temperature of 1g of a substance by 1°C. This is separate from the latent heat values for phase changes. Through these concepts, we can understand and calculate the heat absorbed or released during the phase changes of various substances.