Why does pressure increase when volume decreases?

Hint: Before we get an answer to this question let’s understand pressure and volume. Pressure is the force which is exerted on the object by something in contact with it. Volume is defined as the amount of space that an object or a substance occupies. Now let us solve the given question.

Complete step by step solution:
Consider Boyle’s law which gives the relation between pressure and volume. It states that at a constant temperature the volume of a gas varies inversely with the pressure exerted on it. Let’s see how the volume of a gas decreases when the pressure is increased. Assume that you have taken a mixture of gas in a large container, there are a number of gas molecules in there which try to push the walls of the container thereby creating pressure.

Now reduce the volume of the container, then, the gas particles are now restricted to move in a smaller volume but still exert the same pushing force (due to the same amount of gas being present) and hence increasing the pressure. Consider another example. Let us assume we have a box half-filled with soft candies. Let this be a substitute for the molecules within a material.

Now, let us start shrinking the box’s volume by 1% for every second. So, with the reduction in the volume of the box, the candies start getting closer together. By the time the box is reduced to the size of a matchbox, the candies will all be crushed together (hence leading to the higher density of the candy). Reduction in volume leads to higher pressure and higher density.

Note:If the volume remains constant (in a closed container) the temperature increases thereby increasing the pressure. The temperature increases because the movement of the atoms increases leading to an increase in the pressure.