Hot air

[palaniyapan]

Why does hot air rise?

[bernardo]

Because it's less dense.  Or more to the point, cold air is less dense.  The dense cold air is so heavy that it wants to fall, and pushes the hot air up to get out of the way.  It's the same reasons why bubbl;es rise in fizzy drinks - intuition says that the rise of the bubbles is against the law of gravity, but actually it is the liquid falling rather than the bubbles rising.

[bernardo]

Because it's less dense.  Or more to the point, cold air is more dense.  The dense cold air is so heavy that it wants to fall, and pushes the hot air up to get out of the way.  It's the same reasons why bubbl;es rise in fizzy drinks - intuition says that the rise of the bubbles is against the law of gravity, but actually it is the liquid falling rather than the bubbles rising.

[Spot the difference]

[richb14]

You said cold air was less dense on the 1st!

[jno]

yes, but it's the first answer that got 3 stars, so palaniyapan may be in for a shock