# 12.1 Experimental gas laws

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## Pressure

= force per unit area that a gas exerts on a surface. Measured in Pascals.

I Pa = 1 Nm-2

Dependent on the temperature, volume of gas container and mass of gas.

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## Boyle's law

The gas pressure x it's volume is constant providing the mass and temperature remains the same.

A change at constant temperature = isothermal change.

If you plot a graph of pressure against 1/volume, you get a straight line as pV= constant equals p = constant x 1/V.

pV = constant

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## Charles' Law

• Plotting the measurements of the volume of a gas at 0 and 100 degrees Celsius, shows absolute zero is -273.15 degrees whatever volume used.
• This graph is a straight line passing through the axis at (absolute) zero, therefore:

V/T = constant

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## The pressure law

• The pressure of a fixed mass and volume of gas is measured when temperature is increased.
• The measurements are plotted an they give a straight line through the origin therefore:

P/T = constant

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