When you roll one ball into another ball that
is sitting still, the ball that was originally still will start rolling
 but the other ball will slow down. We can think of a hot gas as many tiny balls, moving very
quickly and a cool gas as many tiny balls, moving very slowly.
This way of thinking about gasses is often called the "Billiard
Ball Model" of gas.
What would happen if you mixed a hot gas and a cool gas together? Try to explain your answer using the Billiard Ball Model. What would happen if you mixed a hot gas with twice as much cool gas? Try to explain your answer using the Billiard Ball Model.


Before going on to the next page  write down what you think happens when you mix a hot gas with a cool gas, then go on to Activity 5 (outside site) to watch an animation of gasses mixing.  