Question

how is hot air lighter than the cold air​

Answer 1

When the air expands, it becomes less dense than the air around it. The less dense hot air then floats in the more dense cold air much like wood floats on water because wood is less dense than water. Because the cold air contains some of the molecules of water. ... So warm air is lighter than cold air

Answer 2

Answer:

Hot air rises because when you heat air (or any other gas for that matter), it expands. When the air expands, it becomes less dense than the air around it. The less dense hot air then floats in the more dense cold air much like wood floats on water because wood is less dense than water. This floating effect in a less dense medium is called a buoyant force or a displacement force