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Why does warm air rise and cool air sink during natural convection?
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heat
What's the relationship between heat and temperature?
In natural convection, the movement of air is driven by changes in density resulting from temperature differences.1
When air is heated, its molecules move faster and spread farther apart, causing the air to expand and become less dense. Because of this increased buoyancy, the warmer, less dense air rises. Conversely, as air cools, its molecules slow down and move closer together, which increases the density of the air and causes it to sink.12
This continuous cycle of rising warm air and sinking cool air establishes a convection current, which serves to redistribute heat and promote more uniform temperatures within a fluid system.12