Question

In convection process rate of heat transfer is compared in the option between gas and liquid, choose the correct statement:
(A) gas convects more as compared to other
(B) liquid convects more as compared to other
(C) liquid convects more as compared to other only if certain factors assists water
(D) none of the above:

Answer 1

Hint: Convection is due to a density differential within a fluid. Liquids have less intermolecular separation than gases. This information will lead to the answer.

Complete step by step answer:
In liquids and gases, heat transfer occurs by convection process as their molecules have more intermolecular separation compared to solids and move freely. With increase in temperature, the fluid becomes less dense, and rises, thereby setting convection currents.
In liquids, the molecules are closer to each other as compared to in the gases. Hence, the liquid molecules convect more readily than gaseous molecules that have maximum intermolecular separation between them.
Water has maximum density at temperatures \[{{0}^{\text{o}}}\text{C}\] and \[{{4}^{\text{o}}}\text{C}\]. Therefore, at these temperatures the convection rate decreases. However, when the density of water is normal, that is, at room temperature, the convection rate is fast. So liquid convects more than gas only if water is at room temperature.

So, the correct answer is “Option C”.

Note: Convection may be defined as the transfer of thermal energy by the motion of a fluid or within a fluid, that is, within a liquid or a gas. The heat transfer takes place by actual movement of material particles carrying heat from one place to another.
The phenomenon of convection has a large number of applications in daily life, such as ventilation, domestic hot-water system, central-heating system, steam heating, chimneys used in factories, green houses, etc.