# why is warm air less dense than cold air?

Relevance

When air is heated up, the particles vibrate and move further apart, so for a fixed mass of gas, the volume increases (greater amplitude of vibrations means they take up more space).

Since the formula for density is: Density= Mass/ Volume

If you keep the mass constant, you can say that "the density is inversely proportional to the volume". This means that is the volume increases (as with warm air), it's density decreases.

• 4 years ago

As the guy above me said, it is physics. The heat spreads over the thinner air and becomes very cold. As for the High Pressure and Low pressure, what you said is not necessarilly true. Durring a heatwave, a swath of ho air creeps north as a High Pressure system. Also durring heatwaves, it is common to find severe storms forming near the jet stream sepparating the fronts or just popping up anywhere at NIGHT because as temps cool, that cold air mixes with the hot air and it becomes a battlefield. The closer you are to water, the more rain these storms will bring which is why it is a bigdeal on the East Coast. Second, Low Pressure systems don't always bring warm weather. In June of this year, A stationary front (consisting of Low Pressure) brought the North East temperatures 10-15 degrees below normal and constant rain for most of the month. The jet stream below prevented any warm air from creeping in. It really just depends ont he situation at hand is.

• Anonymous

As the air gets warmer, the molecules get more kinetic energy and move faster. This means that they will need to occupy a larger volume to maintain a constant pressure. As the number of molecules of air particle (the mass of the air) hasn't changed, the density will drop because D = mass / Volume.

• 3 years ago

What Is Warm Air

Density is mass /volume

D=M/V

Mass remains constant, but if you heart the gas, at the same pressure, it must increase in volume.You are therefore dividing the constant M by a larger V, so the resulting D must decrease