Q3. A teacher demonstrated the relationship between the pressure in a gas and the volume of the gas.
The figure below shows the equipment used.

This is the method used.
1. Record the initial volume of gas in the syringe and the pressure reading before any weights are attached.
2. Attach a 2.0 N weight to the syringe.
3. Record the volume of the gas and the reading on the pressure gauge.
4. Repeat steps 2 and 3 until a weight of 12.0 N is attached to the syringe.
(a) What was the range of force used?
From __________ N to __________ N
(1)
(b) Give one control variable in the investigation