Physics P3 Edexcel: Gases

Contains useful notes, equations and revision questions on the Kelvin scale, pressure and temperature in gases etc.

P3 Topic 5: Particles in Action

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  • Created by: Tiula
  • Created on: 16-01-10 11:11
Preview of Physics P3 Edexcel: Gases

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Particles in a gas randomly move about. They are constantly colliding with one another and
bouncing off the walls of their container (e.g. the gas syringe, test tube, room etc).
If you increase the temperature the particles have more energy, so they move about more quickly.
The coldest anything can ever get is -273oC (absolute zero). At absolute zero they have no kinetic
energy and do not move at all.
Absolute zero is also 0 degrees on the Kelvin scale. This is the same as centigrade, but the zero is in a
different place:
Centigrade -273 oC 0 oC 100 oC
Kelvin 0K 273K 373K
If you double the temperature of a gas (in Kelvin), the kinetic energy is doubled too. The posh way
of saying this in an exam is: the temperature of a gas in K is proportional to the kinetic
energy of the particles.
When particles bash into the walls of the container this creates pressure. The faster the particles are
going, the higher the pressure because a) they collide with more force and b) they collide more
So: if you heat a gas, the particles move faster (more KE) and there is higher pressure.
(P1 x V1) / T1 = (P2 x V2) / T2
Example question:
A container has a volume of 30 litres. It is filled with gas and has a pressure of 1 atm and a
temperature of 17oC. If the temperature is increased to 42oC, what is the new pressure?
First, make the temperatures into Kelvin. So: 17oC becomes 290K and 42oC becomes 315K.
Next, put it into the equation above.
(1 x 30)/290 = (p x 30)/315

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