Search the World of Chemistry×
25th Dec 2019 @ 4 min read
Boyle's law is a pressure versus volume relationship. The law was discovered by Robert Boyle in the 17th century. It states the pressure of a fixed amount of a gas is inversely proportional to its volume at a constant temperature. The law can be empirically proven. The article discusses an experimental method to verify the law using a syringe.
The experiment is very simple. It can be performed at home. When the tip of a syringe is sealed with a cap, the air inside the syringe is isolated from the atmosphere. This will fix the amount of the gas. The weights (books) are added upon the plunger of the syringe. It will push the plunger downwards; in other words, the air in the syringe is compressed. By recording the weights of the books added and the volume reading from the syringe, we can establish the pressure-volume relationship.
To verify Boyle's law and to plot the pressure-volume graph
The initial weight (w0) is 92 g.
The total weight is .
The observation table is as follows:
|No. of books||Volume reading in mL (Vi)||Average (Vi)||Weight in g (wi)||Total weight in g|
|Set 1||Set 2||Set 3|
The pressure on the air inside the syringe is the pressure exerted by the weights plus atmospheric pressure.
The pressure exerted by the weights is the force exerted by the weights divided the inner area of the syringe.
Now, Force (Fw) is mass (Wi) times acceleration (a).
Here, r is the inner radius of the syringe, which can be measured; r = 0.005 m. a is the acceleration due to gravity; a = 9.81 m s−2.
For Wi = 92 g,
Assume atmospheric pressure (Patm) as 101.325 kPa.
Similarly, we can calculate the total pressure for the rest.
The calculation table is as follows:
|No. of books||Pw in kPa||Pi in kPa||Vi in mL||PiVi|
We have to plot the graph of Pi vs Vi and PiVi vs Vi.
The Pressure vs volume graph is as follows:
The pressure-volume vs volume graph is as follows:
The PV curve from the above figure is satisfactory. As the pressure of the air increases, its volume decreases. The air obeys Boyle's law. Also, the product of pressure and volume approximately constant and its value is independent of volume or pressure.
Also, check a laboratory method: To verify Boyle's law»
Copy Article Cite
Join the Newsletter
Subscribe to get latest content in your inbox.
We won’t send you spam.