What Is Conduction & Convection?

Conduction

• When matter is heated, its molecules move faster. Conduction transfers heat by moving molecules without moving the matter the molecules comprise. So, when a hot substance is touching a cool substance, the fast-moving molecules in the hot substance bump into the slower-moving molecules in the cool substance. The faster molecules transfer some of their energy to the slower molecules. The slower molecules speed up and heat up and the faster molecules slow down and cool down. Thus, both objects approach the same temperature.

Convection

• Convection transfers heat through the movement of liquids and gases. Areas of a liquid or gas that have been warmed by a heat source become more buoyant and rise into cooler areas, carrying warmth upward. The cooler, denser areas move out of the way, falling downward toward the heat source. The cycle repeats creating convection currents.

Examples

• An example of heat transfer by conduction is when hot coils on a stove heat up a cold pan. Another example is the way the handle of a hot pan feels against the skin. In both cases, heat is transferred from one substance to another because they are in direct contact. An example of heat transfer via convection is boiling water. The bubbles that rise to the top are the hotter areas of the water moving upward. Another example is the way a space heater warms a room. Hot air moves away from the space heater allowing cooler air to then be warmed. In both examples, moving liquids and gases create convection currents.

Convection and the Weather

• Clouds form when water vapor rises via the air and condenses high in the atmosphere. When the vapor condenses, it releases heat, causing more air to rise, carrying more water up into the forming cloud. The cycle repeats and the cloud grows larger. Thunderstorms can arise from convective clouds. Meteorologists track convection currents to try and predict the locations of thunderstorms and severe weather. Using sophisticated radar systems and analysis algorithms as well as intuition, meteorologists can anticipate convection currents and issue forecasts based on the weather they are likely to produce.