Question

The given figure represents the arrangements of molecules in different states of matter. Which of the following statements are correct?
I - Processes P, Q, R, S, and T are reversible.
II - Processes P, Q, and S involve absorption of heat.
III - Processes R, S, and T involve evolution of energy.
IV - Processes P, R, and S involve absorption of energy.

Answer 1

• Processes P, Q, R, S, and T are reversible as these processes involve change in state of a substance which can be reversed by heating or cooling.
• Process ‘P’ represents conversion of solid to gas by the absorption of heat. This process is called sublimation. Camphor is an example of a solid that sublimes directly into its vapour.
• Process ‘Q’ represents evaporation i.e., change of state from liquid to gas by the absorption of heat.
• Process ‘R’ represents condensation i.e., conversion of gas to liquid on cooling.
• Process ‘S’ represents melting i.e., change of state from solid to liquid by the absorption of heat.
• Process ‘T’ represents conversion of liquid to solid by the evolution of heat. This process is called freezing.
• So, processes P, Q and S involve absorption of energy.Thus, option B is the right answer.