A sample of a pure compound is contained in a closed, well-insulated container. Heat is added at a constant rate and the sample temperature is recorded. The resulting data is sketched below. Which of the following conclusions is justified from the data given?

Question

TestHub · Accepted Answer

The graph has two flat parts: roughly 3 to $9 min$ (melting), and $14 min$ onward (boiling).
(A) The final flat part is boiling, so the sample boiled.
(B) The melting flat part is shorter than the boiling flat part, at constant rate:
$L_{f} < L_{v}$
(C) At $5 min$ melting has begun, so solid and liquid are present.
(D) At $20 min$ the sample is boiling, so it is liquid and vapour.

Physics - Heat & Thermo Question with Solution | TestHub

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