Question

When you heat a bowl of water, we can observe that water starts circulating. This demonstrates:
A. Conduction
B. Convection
C. Radiation
D. None

Answer 1

Hint: when we boil water, the heat from the burner will go to the water that will heat the water at the surface of the bowl. The density of hot water will decrease, therefore, it will rise and the cooler water at the top of the bowl moves down, causing a circular motion in the water.

Complete step by step answer:
When we heat a bowl of water, we will observe that the water will start circulating in the bowl. Thus is the process of convection. Convection is defined as the transfer of heat from one place to another when molecules move in bulk within the fluids.
When the water is heated, the water molecules present above the surface of the bowl will be heated first. Now, as the temperature and density are inversely proportional to each other, therefore, the density of water decreases with an increase in temperature. Now, the density of water present at the surface of the bowl decreases, hence, these molecules will move up and the water present at the top of the bowl will move downwards because of high density.
Therefore, the circulation of water demonstrates convection.

So, the correct answer is “Option B”.

Note:
We can observe the process of convection in the radiator, steam in a cup of tea, ice melting, and frozen food thawing.
Also, in meteorology, convection is the transfer of heat and other properties of the atmosphere when there is a movement of the mass of the air. This transfer will be in an upward direction whereas in geology, convection is the slow movement of the materials present under the Earth’s crust.