Why is warmer air lighter than cooler air?

Question

Anyone know?

Answer 1

same happens with water
warm/ hot water is lighter than cold water !!!!

Answer 2

The heat makes the molecules of a compound to move away from each others. Thus in the same volume we will have less molecules, this is why warmer air is lighter than cooler air.

Answer 3

The air is a fluid, that effect is all based on the density.
For most fluids, density is a function of several factors, among them is the temperature.
At a higher temperature, you get lower density, so the warmer air being less dense, goes up, and is replaced by the cooler air.

It's the same for water, oil, etc.
The decrease of density is because that with heat, the molecules of air move a lot faster, occupying more space while they push the other molecules in the surroundings, so in more space there are less molecules and thus the density decreases (mass per volume unit).

Answer 4

It isn't necessarily. As you rise in the troposphere, the air gets cooler so you have cold air overlying warmer air without sinking and replacing it. Denser air sinks, less dense air rises.This means that the air higher in the troposphere is less dense even though it is colder. The reason for this is that there is less mass of air in the same volume as you get higher so it becomes less dense regardless of the temperature.

If you start with two parcels of air of the same mass per volume and heat one of them, it will expand thus increasing the volume for the same mass and therefore becoming less dense. In this case the warmer air is less dense, and therefore lighter than the colder air.

Answer 5

warmer air has more energy than colder air. that means the gas molecules are moving faster, and when they collide with each other, they push off with more force. this causes the air to be less dense, because the molecules are trying to spread out.

Answer 6

The thermal energy simply causes the air to expand - less molecules and atoms of air for a given volume means less weight.