Why does air heat up when compressed?

Answer 1

Adding heat to an object is essentially adding energy. When energy is added to a gas, the individual molecules of the gas begin to move faster and bounce off of each other and the container the gas is in. The more energy added, the more they bounce and the faster they move. This causes the gas to expand, which increases the pressure inside the vessel.

Answer 2

Through Adiabatic processes The first law of thermodynamics with Q=0 shows that

all the change in internal energy is in the form of work done. The ratio of the specific

heats γ = CP/CV is a factor in determining the speed of sound in a gas and other

adiabatic processes as well as this application to heat. This ratio γ = 1.66 for an

ideal monoatomic gas and γ = 1.4 for air, which is predominantly a diatomic gas.

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Answer #2:

Answer #1 is elegant, as well as true, informative, and excellent.

But my kids want something they can feel. The way I explain it to them is:

You have to spend energy (do work) on the air in order to compress it ... either

pushing and squeezing more air into the same bottle, or pushing and squeezing the

same air into a smaller bottle. All that energy has to go somewhere. It becomes

heat energy in the gas. When you let the gas push on something movable, the

pressure will do work: It'll move the thing it's pushing on. The energy to do that

work comes out of the compressed air, it gets less compressed, and it gets cold.

Answer 3

When air is compressed, its molecules are forced closer together, which increases the number of collisions between the molecules. These collisions result in an increase in kinetic energy, which manifests as an increase in temperature. This is known as the adiabatic heating effect of compression.