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Verification of Charles' law for an ideal gas


The aim of this experiment shows how a gas behaves when it is heated at constant pressure. The law it obeys is called CHARLES’ LAW.


a 0 - 100oC thermometer
a tall 1 litre beaker
a glass capillary tube containing air sealed in with an oil and sulphuric acid plug and closed at one end
2 rubber bands
a bunsen
gauze and mat


Fill your beaker with cold water.
Fix the glass capillary tube to the thermometer with the rubber bands with the open end at the top. The bottom of the tube should be level with the -10 oC mark on the thermometer.


Put the thermometer and tube in the water, the open end of the tube should be just above water level. Record the water temperature.

Record the volume of the trapped air in the tube, you should record this as a number of thermometer divisions. (Remember it starts at -10o).

Light the bunsen and heat the water to boiling slowly. Take readings of the volume of the air every 10 oC and record them. When the water boils turn off the bunsen.


You should record a table as set out below:

Volume of trapped air
Temperature of trapped air

(In the example shown the volume is about 24 units and the temperature 22oC.)

Plot a graph of volume against temperature starting at 0oC. (A)
Plot a further graph showing -350 oC to +100 oC. (B)

Find where your line cuts the temperature axis - this is ABSOLUTE ZERO.

Find out the increase in volume for a 10 oC rise in temperature from your graph and hence calculate the increase in volume per degree centigrade ?

Write up the experiment.

Record any sources of error which you consider will affect your result and suggest how they might be reduced.

SAFETY CONSIDERATIONS: The capillary tube contains a plug of sulphuric acid sealed in with oil. Do not open the lower end of the tube. Wear eye protection. Only heat the capillary tube when it is immersed in the water

Note: Your teacher may wish to give you additional instructions before you carry out the experiment.
© Keith Gibbs 2013