## Demonstration of gas laws

Boyle’s law

Demonstration : Boyle’s Law If you have ever tried to force in the plunger of a syringe or a bicycle pump while sealing the opening with a ﬁnger, you will have seen Boyle’s Law in action! This will now be demonstrated using a 10 ml syringe.

Aim: To demonstrate Boyle’s law.

Apparatus: You will only need a syringe for this demonstration.

Method:

1. Hold the syringe in one hand, and with the other pull the plunger out towards you so that the syringe is now full of air.
2. Seal the opening of the syringe with your ﬁnger so that no air can escape the syringe.
3. Slowly push the plunger in, and notice whether it becomes more or less diﬃcult to push the plunger in.

Results: What did you notice when you pushed the plunger in? What happens to the volume of air inside the syringe?

Did it become more or less diﬃcult to push the plunger in as the volume of the air in the syringe decreased?

In other words, did you have to apply more or less pressure to the plunger as the volume of air in the syringe decreased?

As the volume of air in the syringe decreases, you have to apply more pressure to the plunger to keep forcing it down.

The pressure of the gas inside the syringe pushing back on the plunger is greater.

Another way of saying this is that as the volume of the gas in the syringe decreases, the pressure of that gas increases.

Conclusion: If the volume of the gas decreases, the pressure of the gas increases. If the volume of the gas increases, the pressure decreases. These results support Boyle’s law.

Charles’s law

Demonstration : Charles’s Law

Aim: To demonstrate Charles’s Law using simple materials.

Apparatus: glass bottle (e.g. empty glass coke bottle), balloon, bunsen burner, retort stand

Method:

1. Place the balloon over the opening of the empty bottle.
2. Place the bottle on the retort stand over the bunsen burner and allow it to heat up. Observe what happens to the balloon.

WARNING: Be careful when handling the heated bottle. You may need to wear gloves for protection.

Results: You should see that the balloon starts to expand. As the air inside the bottle is heated, the pressure also increases, causing the volume to increase. Since the volume of the glass bottle can’t increase, the air moves into the balloon, causing it to expand.

Conclusion: The temperature and volume of the gas are directly related to each other. As one increases, so does the other.