A sample of a pure substance, initially in the gaseous state, is cooled at a constant rate. The graph shows how the temperature of the sample varies with time.
Which row in the table correctly describes the behaviour of the average kinetic energy of the molecules, the average potential energy of the molecules, and the total internal energy of the system during Region X?
| Average kinetic energy of molecules | Average potential energy of molecules | Total internal energy of the system | |
|---|---|---|---|
| A | Decreases | Constant | Decreases |
| B | Constant | Decreases | Decreases |
| C | Constant | Constant | Constant |
| D | Decreases | Decreases | Constant |
Row A
Row B
Row C
Row D