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Kinetic Molecular Theory

Pressure-Volume Relation


How does the pressure of a gas depend upon the volume of the gas?

For a fixed amount of gas at a constant temperature, Boyle's Law states that the quantity P V is a constant. (P is the pressure and V is the volume.) Does the Kinetic Molecular Theory correctly predict this behavior?

Start the simulation shown below. The pressure-volume data is plotted on the graphs at the lower right.

Slowly drag the top barrier to change the volume of the system. The new pressure-volume data will be automatically plotted.


1. Does the system obey Boyle's Law?

2. What property of the gas causes the change in pressure when the volume is changed?

Bear in mind that the temperature of the system is held constant. Consequently the average kinetic energy of the particles does not change when the volume changes. The mass of each particle is also held constant. Thus the average speed of the particles and the average force exerted on a wall during a collision are independent of the volume. Carefully examine the behavior of the particles at a small volume and at a large volume. What properties of the gas do change with a change in volume?

Pressure of a Gas                     Pressure-Temperature Relation

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