If you seal the end of a syringe and push on the plunger, is that process isothermal? If so, explain why. If not, explain what you might do to make it isothermal?

1 Answer
Feb 16, 2017

If you seal air in a syringe and push rapidly on the plunger, the process is not isothermal.


Air is a real gas, and the molecules of real gasses are attracted to each other.

If you rapidly compress the air and force its molecules closer to each other, their intermolecular attractions will be stronger and they will be at lower energies.

The excess energy is given off as heat.

Thus, the gas in the syringe will warm up when it is compressed.

One way to keep the process isothermal is to compress the gas so slowly that the excess heat has time to be transferred to the surroundings,


A diesel engine works by the rapid compression of air.

It takes in the air, compresses it, and then it injects the fuel directly into the cylinder.

The compressed air is so hot that the fuel ignites without a spark plug.