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Boyle’s law


Investigate pressure and volume that vary inversely if temperature is held constant.

HOW DOES IT WORK?                                                                     

Time Allocation: 45 Min

To understand the world around us, we have to understand the behaviour of  Gases which have special properties that solids and liquids do not have.

The theoretical description of gases is called the kinetic theory of gases. Scientists need only four quantities to describe gases. These macroscopic [properties arepressure (p), temperature (T), volume (V) and amount of gas (n, mole). Macroscopic properties can be measured physically and provide information about the microscopic properties of gases.

Due to the great number of gases on earth, it is impossible to describe the behaviour of each gas on its own. To simplify this task, scientists decided to create an imaginary gas which is an approximation of the behavior of all real gases on earth – this gas is called an ideal gas. Real gasses show the behavior of ideal gases under normal temperatures and pressures, but deviate from ideal gas behaviour at very low temperatures and high pressures.


  • Boyle’s Law apparatus
  • Graph paper


  1. Use volumes that go up in 4ml graduations.
  2. Note that you should not work according to the numerical graduations on the Syringe of the apparatus, you should go up in 4ml quantities and not according to 60ml quantity on the syringe as to not cause any confusion in results.
  3. You will compress the gas slowly to these volumes and record the resulting pressures.
  4. Record the pressure to the nearest 0.1 psi for each 4ml of pressure applied.
  5. Repeat the process at least 4 times to obtain enough readings, one reading should be of the psi obtained at 0ml with no pressure applied.
  6. Fill in the readings in below table for pressure (kPa) and volume (vol).
  7. Draw a line graph representing the 5 readings of pressure vs volume.


Fill in the readings on the following table:

kPa Vol
Reading 1
Reading 2
Reading 3
Reading 4
Reading 5


Draw a line graph representing the 5 readings of pressure vs volume:


  • Do not increase the pressure on the gas in the tube to extreme values – it can damage the apparatus.


Boyle’s Law has been verified in this experiment. The graph of volume against pressure is a hyperbola and volume against the inverse of pressure is a straight line through the zero point. Both the graphs prove the relationship: V ∝ 1/p. The Law states that the volume of an enclosed gas is inversely