Question

which of the following occurs when a substance changes its state of matter (e.g., from a liquid to a gas or from a solid to a liquid)?
a. the amount of heat does not change, but the temperature changes.
b. the amount of heat changes, but the temperature does not change.
c. both the amount of heat and the temperature change.
d. neither the amount of heat nor the temperature changes.

Explanation:

During a phase - change (state of matter change) like melting or boiling, heat is absorbed or released to break or form intermolecular forces. The temperature remains constant during the entire phase - change process as the energy is used for changing the state rather than increasing the kinetic energy (temperature).

Answer:

B. The amount of heat changes, but the temperature does not change.