Heat caused the water to become a gas. Heat melted the water and it disappeared. Salt caused the water to become a gas. Salt melted the water and it disappeared.
I gave my students this multiple choice question: On a warm sunny afternoon, ocean water splashed onto a rock. A short time later, the rock was dry. Which statement best explains what happened to the water on the rock?

Only one answer is correct among these 4 choices:
- Heat caused the water to become a gas.
- Heat melted the water and it disappeared.
- Salt caused the water to become a gas.
- Salt melted the water and it disappeared.

Could you tell me which one is correct?

Heat caused the water to become a gas.