15 Ideal Gases

The number of atoms or molecules (the amount of substance) in a given volume of gas using moles.

1 mol of any substance contains 6.02 x 10^23 (The Avogadro constant)individual atoms or molecules.

The Kinetic Theory of Gases is used to describe the behaviour of the atoms or molecules in an ideal gas

• The gas contains a very large number of atoms or molecules moivng in random directions with random speeds.
• The atoms or molecules of a gas occupy a negligible volume compared to the gas.
• Collisions of atoms or molecules with each other and the container walls are perfectly elastic (no kinetic energy is lost)
• Time of collisions between the atoms or molecules is negligible compared to the time between collisions.
• Electrostatic forces between atoms or molecules are negligible expect during collisions.

A large number of atoms collide randomly with the walls of the container exerting a force over an area of the container which is its pressure.

pV = nRT  where p = pressure V= volume  n = number of moles  R = Universal Gas Constant     T= Absolute Temperature

Boyle's Law - Pressure of a given mass is inversely proportional to its volume at a constant temperature.

Investigation of Boyle's Law -  A student would slowly decrease the pressure of pressuried, due to this the volume would increase. This shows the inverse proportion relationship between pressure and volume. 

Estimating Absolute Zero

By using a water bath, a heater and flask containing dry air. Slowly decrease the temperature which will decrease the pressure. The absolute temperature will be reached when the pressure gauge drops down to zero.

pV = 1/3 x Number of particles in the gas x mass x mean square speed

k = molar gas constant/Avogadro's constant 

pV = NkT

1/2mc^2 = 3/2 kT

Internal Energy of an ideal gas 

Internal Energy = KE + PE

Electrostatic forces are negligible expect during collisions. So there is no electrical potential energy between gas particles so the internal energy will equal to its kinetic energy. Doubling the temperature therefore doubles the kinetic energy and therefore doubling the internal energy.