The quantity of heat required to convert 5kg of ice at its melting point to water without a change of temperature is

Analysis

The question asks for the specific quantity of heat required to change the state of a substance (ice to water) at a constant temperature.

Concept Explanation

In physics, when a substance changes state (e.g., from solid to liquid) without a change in temperature, we refer to this as a phase change. The heat involved in this process is called Latent Heat.

• Latent Heat of Fusion: This is the total amount of heat required to change a specific mass of a substance from solid to liquid at its melting point. The formula is $Q = mL_f$, where $Q$ is the quantity of heat, $m$ is the mass, and $L_f$ is the specific latent heat of fusion.
• Specific Latent Heat of Fusion: This is the amount of heat required to change unit mass (1kg) of a substance from solid to liquid at its melting point.
• Heat Capacity: This is the amount of heat required to raise the temperature of an object by 1 Kelvin or 1 degree Celsius.
• Specific Heat Capacity: This is the amount of heat required to raise the temperature of 1kg of a substance by 1 Kelvin or 1 degree Celsius.

Since the question asks for the "quantity of heat" required for the total mass (5kg) to undergo a phase change, we are looking for the Latent heat of fusion.

Step-by-Step Solution

1. Identify the process: The ice is at its melting point and is turning into water. This is a phase change, not a temperature change.
2. Eliminate incorrect options: • Options A and C involve temperature changes, so they are incorrect. • Option B refers to the heat required for unit mass (1kg), but the question asks for the heat required for the total quantity (5kg).
3. Select the correct term: The total heat required for a specific mass to change state is defined as the Latent heat of fusion.

Conclusion

The correct option is D.

Exam Tip: Remember the "Latent" rule: If the temperature is constant (no change), it is Latent Heat. If the temperature is changing, it involves Specific Heat Capacity.