Particle Model and Pressure

• Describe the motion of molecules in a gas.

  They are in a constant random motion.
• What factor affects the average kinetic energy of gas molecules?

  The temperature of a substance

  The higher the temperature, the higher the average kinetic energy of molecules.
• What effect does temperature have on the pressure of gas?

  Increases
• Why does Pressure increases a temperature increases?

  Kinetic energy of molecules increases

  Collisons between molecules become more frequent

  Greater rate of change of momentum

  Greater force and therefore pressure.
• If Gas A has a low pressure, and if Gas B has a high pressure, what can be said about the rate of collisons in each gas?

  There are more collisons in Gas B as temperature increases
• Describe the force that the pressure of a gas exerts on the walls of its container.

  The net forces acts at right-angles to the container's surface

  The force increases as pressure increases
• Explain how increase in volume decreases the pressure of a gas.

  Molecules become more spread out so the collisons are more infrequent

  This reduces the rate of collisons

  Rate of momentum decreases, and so force extered on the container decreases, resulting in a lower pressure.
• What is the unit for pressure?

  Pascal (Pa)
• What increases when you do work on a gas?

  The internal energy of a gas

  This can also lead to an increase in temperature