The amount of energy required to change a kilogram of ice block into water without a change in temperature is?

1. Analyze the question

The question asks for the specific term used to describe the energy required to change the state of 1 kilogram of a substance (specifically ice to water) at a constant temperature.

2. Explain the concept

In physics, latent heat is the energy absorbed or released by a substance during a change in its physical state (phase change) that occurs without changing its temperature.

• Specific Latent Heat of Fusion ($L_f$): This is the amount of heat energy required to change 1 kg of a substance from solid to liquid at its melting point without a change in temperature.
• Specific Heat Capacity: This is the energy required to raise the temperature of 1 kg of a substance by 1 Kelvin (or 1°C). This involves a temperature change, which contradicts the question.
• Specific Latent Heat of Vaporization: This is the energy required to change 1 kg of a substance from liquid to gas at its boiling point.

3. Show the solution

• The process described is the phase change from solid (ice) to liquid (water).
• The condition "without a change in temperature" confirms that we are dealing with latent heat, not specific heat capacity.
• Since the change is from solid to liquid (melting/fusion), the correct term is the specific latent heat of fusion.

The formula is:

Where:

• $Q$ = Heat energy
• $m$ = Mass (1 kg)
• $L_f$ = Specific latent heat of fusion

4. Identify the answer

Comparing our explanation to the options provided, the correct term is the specific latent heat of fusion of ice. This matches option A.

5. Exam Tip

Memory Trick: Think of "Fusion" as "Fusing together" or "Melting." If you are melting ice into water, you are dealing with the Latent Heat of Fusion. If you are boiling water into steam (vapor), you are dealing with the Latent Heat of Vaporization. Always remember: Latent = Constant Temperature.