Question

A substance on heating, undergoes a rise in its temperature. Then which of the following is/are correct :

• A. Specific heat capacity of the substance increases
• B. Total energy increases
• C. Average Kinetic energy of molecules increases
• D. None of the above

Answer 1

Answer: (B), (C)

The correct options are
B Total energy increases
C Average Kinetic energy of molecules increases

b) Total energy is the sum total of potential (energy associated with the bonds of the molecules) and kinetic(energy associated with the oscillations of molecules about their mean positions) energies of the molecules of the substance. Upon addition of heat, either the bond length between molecules increases (resulting in increased potential energy) or the molecules vibrates with greater oscillations (resulting in increased kinetic energy) and sometimes both happens. Thus the total energy increases.
c) The average kinetic energy of the molecules of the substance depends on its temperature (it is directly proportional to the temperature). Thus when a substance is heated, it gets warm and its temperature increases and so the average kinetic energy of the molecules increases.