Physics U20

P1V1 = P2V2 (Boyles Law)

PV = nRT

PV = NkT

PV = 1/3 (Nm/V) <c^2>

KE = 1/2 m <c^2> = 3/2 kT

<c^2> = mean square speed of molecules.

T = Absolute temperature.

N = nNa

1 mole of CO2 has 6.02 x 10^23 atoms of Carbon and 12.04 x 10^23 atoms of Oxygen.

In an ideal gas,

• There is no intermolecular force, then no work is done against the force. Particle doesn't have potential energy.
• Particles move in random motion.
• All collisions are perfectly elastic.
• Volume of particle is negligible compared to volume of whole gas.
• Time of collision is negligible compared to time between collisions.

Q. Describe the motion of molecules in a gas, according to the kinetic theory of gases.

Random motion refers to movement that occurs in a straight line at a constant speed between collisions.

Q. State what is meant by the internal energy of a system.

Internal energy is the sum of potential and kinetic energy of particles of a system. It is the total energy of particles in random motion.

Q. Explain why, for an ideal gas, the change in internal energy is directly proportional to the change in thermodynamic temperature of the gas.

In ideal gas, there is no intermolecular force. So molecules have no potential energy. Thus internal energy is only kinetic energy of particles, and mean kinetic energy of particles is proportional to thermodynamic temperature of gas.