(5.15-5.22) Ideal gas + Kelvin scale

Explain Brownian motion.

• molecules in a gas are in constant random motion

• they exert forces when they collide

  • with the walls of the container

  • each other

• thereby exerting pressure

What is absolute zero?

0 Kelvin or -273°C

• the coldest temperature possible

• the particles have minimum kinetic energy in their store

What is the Kelvin scale?

A temperature scale starting from absolute 0.

1K = 1°C

°C = K - 273

K = °C + 273

Why does an increase in temperature = increase in average speed of gas molecules?

• increase in temp = increase in Ek store of particles

• which causes either

  • system temp to increase

  • or change of state

• internal energy of gas = sum of Ek of all molecules

• so higher temp = higher Ek of particles

• so they move around faster

What is the relationship between Kelvin temperature and the average Ek of a gas?

Directly proportional

For a fixed amount of gas

at a constant temperature,

what is the relationship between

pressure and volume?

• when volume increases

• pressure decreases

• as molecules collide less frequently

• and over a greater area.

For a fixed amount of gas

at a constant volume,

what is the relationship between

pressure and Kelvin?

• When Kelvin increases

• Ek is higher

• so molecules move faster

• and collide harder + more frequently with the walls

• so pressure rises

State the formula for the relationship between pressure and Kelvin of a fixed mass of gas at a constant volume.

p₁ / T₁ = p₂ / T₂

State the formula for the relationship between pressure and volume of a fixed mass of gas at a constant temperature.

P₁V₁ = P₂V₂