Kinetic Particle Model of Matter (Cambridge (CIE) IGCSE Physics)

Fig. 5.1 shows the apparatus used to observe the motion of smoke particles that are in the air in a box.

Light from a lamp enters the box through a window in one side of the box. The smoke particles are observed using a microscope fixed above a window in the top of the box.

(i) The motion of a single smoke particle is observed through the microscope.

  In the circle shown, sketch the path of this smoke particle.

[1]

(ii) Explain why the smoke particle follows the path that is observed.

[3]

Fig. 4.1 shows a smoke cell. The cell contains smoke particles and air molecules. It is lit from the side. A student views the motion of smoke particles in the cell by using a microscope.

Describe and explain what the student sees when viewing the smoke particles through the microscope.

Drops of water on a warm surface disappear after a short time. State the term used to describe this process. Explain the process, using your ideas about molecules.

name of process: ..........................................................................................................................

  explanation: ..................................................................................................................................

Some gas molecules are in a box at room temperature.

Fig. 3.1 shows the position of some of the molecules and the direction of movement of each molecule.

(i) Describe the movement of the gas molecules.

[2] 

(ii) Describe how the molecules exert a pressure on the walls of the box.

[2]

The gas in Fig. 3.1 is cooled. The gas turns into a liquid then into a solid.

State how the average separation of molecules in the gas is different from the average separation of molecules in the solid.

Describe the movement of the molecules in

(i) a solid.

[1]

(ii) a gas.

[2]

Extended

A closed box contains gas molecules. How does the momentum of the molecules cause them to exert a pressure on the walls of the box?

Fig. 5.1 shows a metal can containing air. The can is sealed with a lid.

The air in the can exerts a pressure of 20 000 N/m² on the lid. The area of the can lid is 0.09 m².

Calculate the force on the lid due to the air in the can.

force = ...................................................... N 

The air in the can becomes warmer.

State and explain what happens to the pressure of the air in the can. Use your ideas about gas molecules.

Fig. 4.1 represents an atom.

Representing atoms by circles approximately the same size as in Fig. 4.1, sketch

(i) on Fig. 4.2, the arrangement of atoms in a crystalline solid,

[1]

(ii) on Fig. 4.3, the arrangement of atoms in a gas.

[1]

Extended

(i) Describe the motion of the atoms in a solid.

[1]

(ii) A sculptor makes a statue from a block of crystalline rock using a cutting tool. Explain why he must apply a large force to the tool to remove a small piece of rock.

[2]

A helium-filled balloon in the room of a house suddenly bursts.

State and explain, in terms of atoms, what happens to the helium from the balloon after the balloon has burst.

Match each description with the correct state of matter in Table 4.1.

Write the correct letter in Table 4.1.

A – Molecules move around freely and are far apart from each other.

B – Molecules vibrate about fixed positions.

C – Molecules move around randomly and are close to each other.

Table 4.1

Some students heat water in a beaker. They measure the temperature every minute. They heat the water for 8 minutes until it boils, and then continue to heat it for a further 5 minutes.

Describe and explain how the temperature of the water changes during the 13 minutes.

Extended Tier Only

A cube of side 0.040 m is floating in a container of liquid. Fig. 3.1 shows that the surface of the liquid is 0.028 m above the level of the bottom face of the cube.

The pressure of the air above the cube exerts a force on the top face of the cube. The valve is closed.

Explain, in terms of air molecules, how the force due to the pressure of the air is produced.

Extended

The density of the liquid in the container is 1500 kg / m³.

     Calculate:

(i) the pressure due to the liquid at a depth of 0.028 m

     pressure = ......................................................... [2]

(ii) the force on the bottom face of the cube caused by the pressure due to the liquid.

     force = ......................................................... [2]

Extended

The valve is opened and liquid is pumped into the container. The surface of the liquid rises a distance of 0.034 m.

     The cube remains floating in the liquid with its bottom face 0.028 m below the surface of the liquid.

(i) Calculate the work done on the cube by the force in (b)(ii).

   work done = ......................................................... [2]

(ii) Suggest one reason why this is not an efficient method of lifting up the cube.

[1]

Extended

A microscope that produces a very high magnification is used to observe the Brownian motion of smoke particles in air.

  Fig. 5.1(a) shows the apparatus used with the microscope. Fig. 5.1(b) represents the view through the microscope and shows one of the smoke particles being observed.

(i) On Fig. 5.1(b), draw a possible path for the smoke particle.

[2]

(ii) Describe how air molecules cause the smoke particle to follow the observed path.

[2]

Fig. 5.2 shows a volume of gas in a cylinder.

The piston in the cylinder is free to move. The piston moves to the left when the temperature of the gas is decreased.

  Explain, in terms of the molecules of the gas, why this happens.

Describe qualitatively, in terms of particles, the effect on the pressure of a fixed mass of gas in a container when there is:

(i) an increase in temperature at a constant volume

[2]

(ii) an increase in volume at a constant temperature

[2]

Extended

Table 1.1 gives a series of pressures and their corresponding volumes, obtained in an experiment with a fixed amount of gas. The gas obeys the law for a fixed amount of gas at a constant temperature.

 Table 1.1 

(i) State the equation linking the pressure and volume at a constant temperature

[1]

(ii) Determine whether these figures indicate that the temperature was constant throughout the experiment.

[2]

Extended

Air is trapped by a piston in a cylinder. The pressure of the air is 7.1 × 10⁵ Pa. The distance from the closed end of the cylinder to the piston is 48 mm.

The piston is pushed in until the pressure of the air has risen to 9.0 × 10⁵ Pa.

Calculate how far the piston has moved.

Extended

Fig 1.1 shows the graph showing how the volume changes with pressure for a gas at a constant temperature

Fig 1.1

Sketch the graph for the same gas at a higher temperature.

Extended

Sketch the graph of

(i) Pressure p against  where V is the volume of a gas. Label this X.

[2]

(ii) The graph in part (i) but with the gas at a higher temperature. Label this Y.

[1]

Extended

The piston in Fig 1.2 is pulled out of the cylinder from position A to position B, without changing the temperature of the air enclosed. Position B is double the length of the distance between position A and the end of the cylinder. The pressure when the piston is at position A is 2.5 × 10⁵ Pa.

Calculate the pressure when the piston is moved to position B.

The fizz in a soda bottle is caused by carbonation. When the soda is bottled, carbon dioxide is added to the liquid to give it a fizzy taste. The carbon dioxide gas is kept in the liquid by the pressure inside the bottle.

When the bottle of soda is opened, state what happens to the pressure inside the bottle and why.

A student is struggling with their revision and has sketched the following graph in Fig 1.1 to represent the change in temperature with volume for a gas at constant pressure.

Fig 1.1

(i) State the mistake made in the student's graph.

[2]

(ii) Sketch a new graph to show the correct relationship between temperature and volume.

[2]

Extended

Fig 1.2 shows two mugs of tea, A and B. They both hold the same volume of tea.

Fig 1.2

State from which mug the tea evaporates quicker. Explain why, in terms of the behaviour of molecules and the process of evaporation.