Question

1. a scientist has a container with a substance inside. at first, the molecules in the substance move away from each other. later, the molecules move around each other. what change did the scientist observe in the substance?

a) before, the substance was a liquid. later, it was a solid.
b) before, the substance was a gas. later, it was a liquid.
c) before, the substance was a liquid. later, it was a gas.
d) before, the substance was a solid. later, it was a liquid.

Explanation:

1. Recall molecular motion for each state:

• Solids: Molecules vibrate in fixed positions, do not move around each other.
• Liquids: Molecules slide/move around each other, are close together.
• Gases: Molecules move freely, spreading away from each other, with large distances between them.

1. Match the description to the states:

• "Molecules move away from each other" describes gas behavior.
• "Molecules move around each other" describes liquid behavior.

1. Match this sequence to the correct option.

Answer:

b. Before, the substance was a gas. Later, it was a liquid.