Convection is one of the three modes of heat transfer, alongside conduction and radiation. It involves the transfer of heat through the movement of fluids, such as liquids and gases. Unlike conduction, which mainly occurs in solids, convection relies on the bulk movement of the fluid particles to carry heat.

One everyday example of convection is boiling water on a stove. As the heat source increases the temperature at the bottom of the pot, the water molecules closest to the heat source become more energetic and start to move faster. This causes them to spread apart, becoming less dense and rising to the top. The cooler water at the top then moves down to take its place, creating a continuous cycle of upward and downward movement. This process, known as natural convection, effectively transfers heat from the bottom of the pot to the rest of the water.

Another example of convection is the heating of a room using a convection heater. These heaters operate by heating the air around them. As the air near the heater becomes warmer, it becomes less dense and rises to the ceiling. The cooler air in the room moves to fill the space left by the rising warm air, creating a convection current. This movement of the air helps distribute the heat throughout the room, ensuring a more even temperature.

Convection can also occur in liquids, such as in the case of ocean currents. The Sun's heat warms up the surface of the ocean, causing the water to expand and become less dense. This warm, less dense water then rises to the surface and moves horizontally toward cooler regions. As the water cools, it becomes denser and eventually sinks back down to deeper depths. This continuous circulation of water, driven by differences in temperature and density, is a prime example of convective heat transfer in fluids.