Pupil sheet · Gases under pressure

Gases under pressure — final check

Name ______________________ Date ____________

Work alone, with the lesson closed. Answer every question; there are no hints.

1. describe / state / explain

A pupil blocks the outlet of a bicycle pump with her finger and pushes the handle in slowly. (a) Describe how the volume of the trapped air changes as she pushes harder. State the two conditions kept the same, so that only the pressure changed. (b) When she lets go, the handle moves back out to where it started. Explain, using kinetic particle theory, why the handle gets harder to push and why it moves back out.

(a) How the volume changes, and the two conditions kept the same

(b) Why the handle gets harder to push, and why it moves back out

2. describe / state / explain / evaluate

An empty plastic drinks bottle (it holds only air) has its cap screwed on tightly at room temperature. It is left in a freezer overnight. In the morning its sides have caved in (bent inwards) a little. (a) Describe what happened to the volume of the air in the bottle. State two things that stayed the same. Because they stayed the same, only the cold could have caused the change. If you name a pressure, say whether it is the pressure of the air inside or outside the bottle. (b) Explain, using kinetic particle theory, why the sides caved in. (c) A pupil says: “The cold made the air particles stop moving and shrink.” Evaluate this statement.

(a) The volume, and two things that stayed the same

(b) Why the sides caved in, using kinetic particle theory