Fig. 2.1 shows a can of compressed air that is being used to blow dust off a computer keyboard. [Figure 2.1]

1. (a)(i)The pressure of the air inside the can is greater than the pressure of the atmosphere. State what is meant by the term pressure.[1]
2. (a)(ii)Explain, in terms of molecules, why the pressure of the air inside the can decreases as it is used.[3]
3. (b)A student uses an inverted measuring cylinder in a water trough to measure the volume that the air occupies at atmospheric pressure. Fig. 2.2 shows the equipment. [Figure 2.2 (not to scale)] Initially the inverted measuring cylinder is full of water. The student presses the top of the can and air passes through the rubber tubing into the inverted measuring cylinder. The air gradually replaces the water in the cylinder until no more air can leave the can. The final temperature of the air is equal to its initial temperature. The volume of the air inside the can is 1.8 x 10⁻⁴ m³. The student observes that, at an atmospheric pressure of 1.0 × 10⁵ Pa, the total volume of the air in the measuring cylinder, the can and the tubing is now 9.4 × 10⁻⁴ m³. Determine the original pressure of the air in the can. pressure = [2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.