Answer the following case-based question:
 
Helen stored a gas inside a cylinder under high pressure. The gas occupies a much smaller volume than it would occupy if it were allowed to spread freely in the surroundings.
 
i. Why can a large amount of gas be stored in a cylinder?
 
ii. Which statement correctly explains the effect of pressure on a gas?
 
iii. When the volume available to the trapped air decreases, the particles: