# Homework Help: Kinetic Theory

1. Apr 21, 2006

### sparsh

Hi

I wanted to know : -

Most gases increase in temperature when they are compressed . Where does the energy for this come from .

When a change of state from liquid to gases occurs is it accompanied by change in the internal energy of the liquid molecules ?

Thanks a lot ..

2. Apr 21, 2006

### Hootenanny

Staff Emeritus
Using the first law of thermodynamics; $\Delta U = Q - W$, $W$ is defined as the work done by the system. Now, when you compress a gas you have to apply a force and since work done is the intergral of force, when you compress a gas you are doing work on the gas. Therefore, you are inceasing the internal energy of the gas and hence the temperature increases.

~H

3. Apr 21, 2006

### sparsh

When a change of state from liquid to gases occurs is it accompanied by change in the internal energy of the liquid molecules ?