Why does warm air rise over cooler air?

Answer 1

Warmer particles are moving faster and less dense (this is why hot air balloons float) then colder particles and rise.

For this reason magma in the Earth is bouyant (Floats) compared to the cooler rock and tends to rise to the surface.

A great example of this effect is a Lava Lamp. The wax near the light at the bottom becomes hot and rises. As it cools it sinks back down.

Most materials tend to go from:

• Solid (Low amount of movement, cool temperatures normally)
• Liquid (medium amount of movement, melting point of a material)
• Gas (high amount of movement, boiling point for most materials)
• Plasma (very high amount of movement, not all materials can potentially hit plasma due to molecular constraints and properties of material)

Ironically ancient civilizations may have already known these 4 states in the form of Earth (Solid), Water (Liquid), Wind (Gas), Fire (Plasma) well over 3000 years ago.

Answer 2

It does not.

Take a volume of air at any given temperature.

If you warm that air, the volume will expand (the air becomes less dense).

If you cool that air, the volume will shrink (the air becomes more dense).

Less dense things float on denser things. Thus where air is warmer than surrounding air (like above a heating radiator) it will rise up.

More dense things sink in less dense things. Thus where air is cooler than surrounding air (like when you open the door of the refrigerator) the cold air will fall out.

From this you will understand that while warm air rises, cold air sinks (not rises as you imply in your question).

Answer 3

warm air is lighter than cold air because the warm air molecules move around faster than cold air molecules

Answer 4

Because hot air is lighter than cold air.