Question

PART A
You have probably seen the heating curve of water. This graph represents a cooling curve of another substance. You can see that over time, the temperature of the substance decreases and the substance changes from a gas to a liquid to a solid. What other information do we know about this substance as it changes?
Responses
A There is a decrease in molecular attraction and kinetic energy.There is a decrease in molecular attraction and kinetic energy.
B Molecules get closer together because there is a decrease in kinetic energy.Molecules get closer together because there is a decrease in kinetic energy.
C Kinetic energy increases while potential energy decreases during the phase changes.Kinetic energy increases while potential energy decreases during the phase changes.
D During phase change there is a drop in temperature along with a drop in kinetic energy and molecular attractive forces.

Answer 1

The most accurate response regarding the changes occurring as the substance cools and transitions from gas to liquid to solid is:

**B. Molecules get closer together because there is a decrease in kinetic energy.**

As the substance cools, the kinetic energy of the molecules decreases, causing them to move slower. This allows the attractive forces between the molecules to bring them closer together, leading to phase changes from gas to liquid (condensation) and from liquid to solid (freezing).

While option A mentions a decrease in kinetic energy, it incorrectly states a decrease in molecular attraction, which actually increases as the molecules come closer together.

Option C is inaccurate because it describes the opposite of what happens during cooling; kinetic energy decreases and potential energy increases during phase changes.

Option D is misleading; while the temperature drops during phase changes, the overall statement about kinetic energy and molecular attractive forces does not accurately reflect the transitions occurring during cooling.

Thus, B is the best choice among the given options.