Question

Assertion

The density of liquids and gases decreases with the rise in temperature.

Reason

With the rise in temperature, the volume of the gases or liquids increases, but not mass. As density is mass per unit volume, therefore, with the increase in volume the density decreases.

Answer 1

Explanation for the assertion statement

1. Due to the rise in temperature, the molecules of the liquid and gas gain kinetic energy.
2. Due to the gain in kinetic energy, the molecules of the liquid and the gas move very much away from each other.
3. Due to the increase in the distance of separation between the fluid and gas molecules, the volume of the fluid and the gas increases.
4. Due to the increase in the volume of the liquid and the gas, the density of the liquid and the gas decreases.

Explanation for the reason statement

1. With the rise in temperature, the volume of the gases or liquids increases because of the gain in kinetic energy.
2. Due to the gain in kinetic energy, the molecules of the liquid and the gas move very much away from each other which increases the volume of the liquid and the gas.
3. Mass is the quantity of matter present in a body and is independent of volume change.

Hence, both assertion and reason are correct and the reason is the correct explanation of the assertion.