Question

State whether the given statement is True or False.
The process of convection can take place only in liquid and gases.
A. True
B. False

Answer 1

We observe three forms of thermal energy transfer in our daily life. They are namely, conduction, convection and thermal radiation. The word thermal is related to things dealing with temperature. We must also consider the property of constant motion of liquid and gases while commenting upon their mode of energy transfer.

Complete step-by-step solution:
Temperature is directly proportional to kinetic energy. Thus, molecules at higher temperature possess higher kinetic energy than the average kinetic energy of the molecules.

Molecules with higher kinetic energy collide with neighbouring molecules with lower kinetic energy and transfer some of their kinetic energy and momentum. This takes place during the process of conduction where the molecules are at rest (mainly in solids).

Convection occurs around the idea that hot substances are less dense than cool substances. Since denser molecules are present around the less dense and hot ones, the hot molecules rise to make space for the comparatively cooler ones to come down near the source of energy and gain some kinetic energy too. Therefore, convection requires the molecules of the substance to be in constant motion and thus occurs in only fluids which are in motion.
Radiation takes place when we have charged particles being accelerated which release electromagnetic radiation. Thus, radiation occurs without any material carrier.

Therefore, the given statement that the process of convection can take place only in liquid and gases is true.

Thus, the correct option is (A) True.

Note:
The reason that any hot entity is less dense than its cooler form is that the molecules of the substance have a much higher kinetic energy. So, they will collide with each other and push each other much further away, getting more separation from each other because of that high average kinetic energy.