IGCSE Physics MCQs 09 - The Kinetic Model of Matter

A liquid is evaporating. The liquid is not boiling.

Which statement about the liquid is correct at an instant in time?

• Any molecule can escape, and from any part of the liquid.

• Any molecule can escape, but only from the liquid's surface.

• Only molecules with enough energy can escape, and only from the liquid's surface.

• Only molecules with enough energy can escape, but from any part of the liquid.

A gas is contained in a sealed container in a laboratory. The temperature of the gas increases.

What happens to the average speed and what happens to the total kinetic energy of the gas molecules?

• Average speed: does not change | Total kinetic energy: does not change

• Average speed: does not change | Total kinetic energy: increases

• Average speed: increases | Total kinetic energy: does not change

• Average speed: increases | Total kinetic energy: increases

Which equation can be used to calculate the pressure at a depth h beneath the surface of a liquid?

A fixed mass of gas is trapped in a container. The temperature of the gas is increased but the volume of the gas is kept constant.

How does this change affect the kinetic energy of the molecules and the pressure on the walls of the container?

• Kinetic Energy: increases | Pressure: increases

• Kinetic Energy: stays the same | Pressure: increases

• Kinetic Energy: increases | Pressure: decreases

• Kinetic Energy: decreases | Pressure: increases

An object is 20 cm below the surface of a liquid. The density of the liquid is 1200 kg/m^3.

What is the pressure on the object due to the liquid?

• 600 Pa

• 2400 Pa

• 60000 Pa

• 240000 Pa

Which statement about the evaporation of a liquid is correct?

• The least energetic molecules escape from the surface and the temperature of the liquid decreases.

• The least energetic molecules escape from the surface and the temperature of the liquid increases.

• The most energetic molecules escape from the surface and the temperature of the liquid decreases.

• The most energetic molecules escape from the surface and the temperature of the liquid increases.

A bubble of gas is formed deep under water. The bubble has a volume of 40 cm^3 and the pressure inside the bubble is P.

The bubble rises up thorugh the water. The volume of the bubble increases to 56 cm^3 and the pressure becomes 100 kPa. The temperature of the gas does not change.

What is the initial pressure P?

• 71 Pa

• 71 kPa

• 140 Pa

• 140 kPa

The density of mercury is 13600 kg/m^3.

What is the pressure at the bottom of a column of mercury that has a height of 75.0 cm?

• 1.02 x 10^4 Pa

• 1.02 x 10^5 Pa

• 1.02 x 10^6 Pa

• 1.02 x 10^7 Pa

Which row describes the arrangement and the motion of the molecules in a gas?

• Arrangement: far apart | Motion: move freely

• Arrangement: far apart | Motion: vibrate only

• Arrangement: tightly packed | Motion: move freely

• Arrangement: tightly packed | Motion: vibrate only

A bubble of air of volume 3.0 mm^3 is under water. The bubble is at a depth where the pressure of the air inside the bubble is four times atmospheric pressure.

The temperature of the air in the bubble stays the same as it rises to the surface.

What is the volume of the air in the bubble as it reaches the surface?

• 3.0 mm^3

• 9.0 mm^3

• 12 mm^3

• 15 mm^3