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CIE iGCSE Co-Ordinated Science P2.1.3 Pressure changes Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

The pressure of a gas in a container is caused by gas molecules colliding with the walls.

The pressure can be increased by heating the gas or by reducing its volume.

Which row explains why the pressure increases in each case?

▶️ Answer/Explanation
Heating the gas gives the molecules more kinetic energy, so they move faster and hit the walls harder and more often.
Reducing the volume packs the same number of molecules into a smaller space, so they hit the walls more frequently, but each collision is no harder since their speed hasn’t changed.
✅ Answer: (B)

Question

Some gas is put in a sealed metal container of constant volume. The gas is now cooled.

What happens to the average speed of the gas molecules, and what happens to the pressure of the gas?

▶️ Answer/Explanation
Cooling a gas reduces the kinetic energy of its molecules, so the average speed of the molecules decreases.
Slower-moving molecules collide with the container walls less often and with less force per collision.
Fewer, gentler collisions per unit area mean the pressure of the gas decreases.
✅ Answer: (A)

Question

A fixed mass of gas is trapped in a container. The temperature of the gas is increased but the volume of the container does not change.

How do the kinetic energy of the molecules and the pressure of the gas change?

▶️ Answer/Explanation
Heating the gas increases the average kinetic energy of its molecules.
Faster-moving molecules collide with the container walls more often and with greater force.
At constant volume, this means the pressure of the gas increases.
✅ Answer: (D)

Question

Gas is trapped in a container.

The piston is moved to the right. The temperature of the gas does not change.

Which statement about the gas is correct?

A. The kinetic energy of the gas particles decreases.
B. The kinetic energy of the gas particles increases.
C. The pressure of the gas decreases.
D. The pressure of the gas increases.

▶️ Answer/Explanation
Moving the piston to the right increases the volume of the container. At constant temperature, the kinetic energy of the gas particles remains constant. With larger volume, the particles have more space to move, so they collide with the walls less frequently, causing pressure to decrease.
✅ Answer: (C)

Question

A gas in a balloon is heated at constant pressure.

What happens to the gas?
(A) Its density decreases.
(B) Its mass decreases.
(C) Its temperature decreases.
(D) Its volume decreases.

▶️Answer/Explanation

Ans: A

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