Question

what happens to the temperature of a substance during a phase change?
it increases rapidly.
it decreases rapidly.
it stays constant.
it varies unpredictably.
which phase change requires the addition of thermal energy?
condensation
freezing
melting
deposition

Explanation:

First Question (Phase Change Requiring Thermal Energy Addition)

Step1: Recall Phase Change Energies

Melting (solid to liquid) needs heat (thermal energy) added. Condensation (gas to liquid) releases heat. Freezing (liquid to solid) releases heat. Deposition (gas to solid) releases heat.

Step2: Identify Correct Option

Only melting requires adding thermal energy.

Step1: Recall Phase Change Temperature

During a phase change (like melting, boiling, freezing, condensation), the temperature of the substance remains constant as energy is used for the phase transition (latent heat), not temperature change.

Step2: Identify Correct Option

So the temperature stays constant.

Answer:

B. Melting (assuming options are A. Condensation, B. Melting, C. Freezing, D. Deposition)

Second Question (Temperature During Phase Change)