Ideal Gases

Boyle’s law

For a fixed mass of ideal gas at constant temperature, the temp of the gas is inversely proportional to its volume

Amonton’s Law

The pressure of a fixed mass and fixed volume of gas is directly proportional to the absolute temperature of the gas

Absolute Zero

The temp when all molecular motion ceases, and the pressure of a gas drops to zero. The accepted value is -273.15°C

Charles’ Law

At constant pressure, the volume of a fixed mass of an ideal gas is directly proportional to its absolute temperature

What is the relationship between pressure, force and area

1 Pa =1N =1$m^2$

Avogadro’s Law

Equal volumes of gases at the same temp and pressure contain the same number of molecules

Boltzmann constant

Fundamental constant that links macroscopic measurements of P, V and T to the microscopic behaviour of particles in a gas.

What does the Boltzmann constant allow

Allows predictions about the way that ideal gases behave on a macroscopic scale

Ideal gas model key features

• Large number of identical, small hard spherical molecules

• Vol molecules is much smaller than Vol container

• Collisions between molecules themselves and the container are elastic and all motion is frictionless (no energy loss in motion or collision)

• All movements of molecules obey Newton’s Law of motion

• Constantly moving in random directions with a distribution of velo about a $\overline{velo}$

How do ideal gases move

Move in random directions

Macroscopic pressure

Force acting over a given area

How are gases arranged in a container

Spread throughout container and fill the available volume

When is the behaviour of real gases close to that of ideal gases

at low pressures

What affect does temperature have on gas molecules

Increases kinetic energy of particles, increases average velocity of particles.

causes higher forces therefore higher pressures.

What is assumed about the volume of particles in the molecular kinetic theory model

Negligible compared to the volume of the container/box

What is crms

“Root mean square velocity”

(The square root of the average of the square velocities)