Topic 8 Kinetic Model of Matter

According to the kinetic theory, matter is made up of very small particles in a constant state of motion. Which best describes the forces and arrangement of the particle behaviour in the gaseous state?

• A. strong forces | particles are close but packing is more disorderly than in a liquid

• B. strong forces | particles are far apart in a disorderly arrangement

• C. weak forces | particles are close but packing is more disorderly than in a liquid

• D. weak forces | particles are far apart in a disorderly arrangement

What describes the volume and shape of a gas or liquid at constant temperature?

• The volume of a gas is fixed but its shape is not fixed.

• The volume of a gas is not fixed and its shape is not fixed.

• The volume of a liquid is fixed and its shape is fixed.

• The volume of a liquid is not fixed but its shape is fixed.

Air in a closed container contains smoke, illuminated by bright light. When viewed through a microscope, bright specks of light are seen moving at random.

• The random motion of the specks is faster in a vacuum.

• The specks move faster when the air is at a higher temperature.

• The specks seen are molecules of air in rapid random motion.

• When the light is turned off, the specks slow down and stop moving.

Smoke particles in air are illuminated by a beam of light and viewed through a microscope. The smoke particles undergo jerky random motion. What causes this motion?

• atomic vibrations within the smoke particles

• collisions between the smoke particles

• impacts of fast-moving air molecules

• the energy of the beam of light

When the temperature of a gas in a container increases, what happens to the pressure of the gas according to ideas about molecules and the definition of pressure?

• The pressure increases because molecules move faster and hit the walls more often and with greater force.

• The pressure decreases because molecules move slower and hit the walls less often.

• The pressure stays the same because temperature does not affect molecular motion.

• The pressure increases because the number of molecules increases.

An experiment to show the Brownian motion of smoke particles in air is illustrated in Fig. 3.1. (a) In the space below, draw the movement of a smoke particle seen through the microscope.

• Random, zigzag movement (Brownian motion)

• Straight line movement

• Circular movement

• No movement at all

State two reasons why collisions between air molecules and smoke particles cause the smoke particles to move randomly.

• 1. Air molecules are in constant, random motion. 2. Collisions transfer momentum to the smoke particles, causing them to move in random directions.

• 1. Smoke particles are heavier than air molecules. 2. Collisions cause the smoke particles to lose energy and stop moving.

• 1. Air molecules are stationary. 2. Collisions have no effect on the movement of smoke particles.

• 1. Smoke particles repel each other, causing random movement. 2. Air molecules are attracted to smoke particles.

The temperature of air inside a closed glass box increases. What happens?

• Air molecules move faster and collide with the walls of the container more frequently and with greater force, increasing the pressure.

• Air molecules move faster and collide with each other more frequently and with greater force, increasing the pressure.

• Air molecules expand and collide with the walls of the container more frequently and with greater force, increasing the pressure.

• Air molecules expand and collide with each other more frequently and with greater force, increasing the pressure.