Melting and Kinetic Energy – Rankers Physics

Calorimetry: Practice Problem & Solution

Assertion (A): Melting of solid causes no change in internal kinetic energy. Reason (R): Latent heat is the heat required to melt a unit mass of solid.  
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Calorimetry. Understanding the underlying formula is key to arriving at the correct answer below:

During melting at constant temperature, the average kinetic energy of molecules (related to temperature) remains constant.

Latent heat increases potential energy. So (A) is true. (R) correctly defines latent heat.

However, (R) does not explain why kinetic energy remains unchanged.

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