Question

reasoning about freedom of movement (continued)
dr flores wants to know which of the forum claims is best supported by the evidence you have gathered from your previous sim observations and the text. select the claim you think is best supported from the options below.
claim 1: molecules in a substance disappear or no longer exist when a substance changes phase.
claim 2: molecules in a substance move differently when a substance changes phase.
claim 3: molecules in a substance change into a new kind of molecule during a phase change.
explain your choice below using evidence you have gathered thus far.

Explanation:

When a substance changes phase (e.g., from solid to liquid or liquid to gas), it is a physical change. In physical changes, the molecules of the substance do not disappear (so Claim 1 is wrong - matter is conserved according to the law of conservation of mass). Also, the molecules do not change into a new kind of molecule (so Claim 3 is wrong - that would be a chemical change). However, the movement of molecules changes. For example, in a solid, molecules vibrate in fixed positions; in a liquid, they can move more freely (slide over each other); and in a gas, they move rapidly in all directions. This is supported by kinetic - molecular theory which describes the behavior of molecules in different states of matter.

Answer:

Claim 2: Molecules in a substance move differently when a substance changes phase.