gases

Convection currents are the result of differential heating. Lighter (less dense), warm material rises while heavier (more dense) cool material sinks. It is this movement that creates circulation patterns known as convection currents in the atmosphere, in water, and in the mantle of Earth.

Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection. Liquids and gases expand when they are heated. The denser cold liquid or gas falls into the warm areas.

Convection is the process of heat transfer that involves the movement of a liquid or a gas. In this case, solids do not undergo convection because their particles are tightly packed; hence, heat transfer using convection cannot happen in this kind of environment.

(Even in the above beaker example, the water molecules, (along with convection) give out heat in the form of radiation as well, as they have a non-zero temperature. However, in that example, convection was the most dominant mode of heat transfer.)

Answer: Radiation is the fastest mode of transfer of heat, because radiation travels at the speed of light, which is very quick. The slowest mode of transfer of heat is conduction because it takes place from particle to particle. Radiation is considered the fastest mode of heat transfer as it travells as fast as light.

Both conduction and convection require matter to transfer heat. Conduction is the transfer of heat between substances that are in direct contact with each other. The better the conductor, the more rapidly heat will be transferred. Metal is a good conduction of heat.