Molecular Interpretations

For a given amount of trapped gas, we can readily observe the effect of pressure on volume with no change in temperature. If we compress a container and force gas particles into a smaller space, then they will collide more frequently with the container even though they still move with the same average speed (same temp). More collisions result in a greater internal pressure. So, if a container under this increased pressure cannot withstand it, then it will crack or maybe explode! If the "system" happens to be some air trapped behind food stuck in a choking victim's trachea, then abdominal thrusts (Heimlich maneuver) are a good way to compress the volume of this trapped air behind the food. This results in more pressure exerted by the air trapped behind the food -- hopefully enough to force the food up and out and save the person (my husband had to do this once in a public restaurant to someone we didn't know… saved her life!). This is all kind of like the motion of a piston in a cylinder...