Use the kinetic molecular theory to explain why a liquid gets cooler as it evaporates from an insulated container.

Interpretation:

           Explanation has to be given for the observation- “A liquid gets cooler when it evaporates from an insulated container”.

Concept introduction:

          The phenomenon of evaporation of liquid is transition from “liquid phase” to “vapo r phase”. Almost all the liquids have the tendency to evaporate either spontaneously at room temperature without the effect of “external energy” or in the presence of external energy like heat etc. Since evaporation occurs by the process of absorbing heat from the surroundings, it is an endothermic process.

          Insulation is a process in which there is no transfer of heat or any other form of energy from one body to the other or surroundings.

Explanation

Understand the concept of “energy” in the molecules.

          At room temperature, many of the compounds do remain in stable state. It means their molecules have low energy levels which contribute to the “stability”.

          A substance containing molecules with a lowest possible energy can have high stability. It implies the molecule has not enough energy to undergo any kind of “physical” or “chemical” changes.

         Energy of the molecules can be distinctly classified as kinetic or potential energy which is stored in the molecules in the form of four types of energy – translational energy, vibrational energy, rotational energy and electronic energy. If a substance is said to be stable then it means all these four types of energies are at their lowest possible levels.

          The molecules in motion possess kinetic energy whereas the molecules at rest possess potential energy. The average kinetic energy possessed by molecules is known as temperature.

          Gaseous molecules, for example, has fast motion at room temperature itself than that of the solid and liquid molecules. Thus, gaseous molecules have more kinetic energy...