Question

24 what number(s) show a change in potential energy? a 5 b 4 c 3 d 1 e 2

Explanation:

• During phase - change (flat - line regions in a temperature - time graph), there is a change in potential energy.
• Region ① and ④ are flat - line regions (phase - change regions). But since ④ is an option (assuming the numbering in the options corresponds to the regions in the graph).

Answer:

B. 4