Malik is investigating the properties of helium. Malik finds the chart below about helium in a textbook.

Malik uses models to study helium as different states of matter. He also investigates the motion of helium molecules.
Multiple Choice Question
Malik draws a model to explain changes of state for helium as shown.

Step X describes how helium gas could become a liquid. Which of the following could be the label for Step X?
A.
Thermal energy is removed and molecular motion increases.
B.
Thermal energy is added and molecular motion decreases.
C.
Thermal energy is added and molecular motion increases.
D.
Thermal energy is removed and molecular motion decreases.
1 answer
To describe how helium gas could become a liquid, you would need to consider the processes of cooling and the behavior of molecules.
When gas turns into a liquid (a process known as condensation), thermal energy is removed, and the motion of the molecules decreases as they come closer together and form a liquid state.
Therefore, the correct label for Step X is:
A. Thermal energy is removed and molecular motion decreases.
