a scientific model using the idea of moving particles to explain the behaviour of matter.

caused by a force acting over an area on a surface; it can be calculated using: pressure = force ÷ area

Explaining pressure changes

Physics

Calculating density and measuring volume

Measuring density

Pressure in a fluid

Upthrust

Explaining convection

In the Energy of moving particles unit, they will build on this knowledge to learn how the movement and nature of different particles transfers energy by conduction, and how specific heat capacity and specific latent heat quantify the effect of heating on the properties of a material.

In the Heating and cooling unit, pupils learnt how the motion of particles in solids, liquids and gases changes when they are heated, how thermal conduction and insulation work and why heating different materials doesn’t always increase their temperatures by the same amount. 

This unit defines density and explores how it varies between states of matter based on atomic arrangement. It covers mass conservation during physical changes, gas behaviour, fluid pressure, buoyancy, and atmospheric pressure, and calculations involving density, mass, and volume relationships.

Particle explanations of density and pressure

It can be used to explain how matter behaves.

It can be used to predict how matter will behave.

The model is made of diagrams or animations.

It says that particles move in liquids and gases but not in solids.

It says that particles in solids, liquids and gases are always moving.

Which of the following statements about the particle model are correct?

There are more particles inside, so their collisions become more frequent.

This increases the outward forces exerted by the air on the balloon.

The outward forces are now greater than the inward forces.

This makes the balloon expand, which increases the volume inside it.

The particles inside are now more spread out, so collisions are less frequent.

This decreases the pressure on the inside of the balloon.

Expansion stops when this balances the air pressure outside.

A child blows air into a balloon. Order the statements to describe and explain what happens.

A gas expands by exerting an average force of 500 N on a piston. This pushes the piston through a distance of 4.0 cm in the direction of the force. The work done by the gas on the piston is {{}} J.

The surrounding air does work on the gas.

The gas does work on the surrounding air.

When some gas is released from a container, the gas expands rapidly. Which of the following statements are correct?

The particles take more time between collisions, on average.

The particles travel less far between collisions, on average.

The particles collide more often with each cm$$^2$$ of the container's surface.

The pressure of the gas on the container increases.

The pressure of the gas in the container halves.

The volume of a sealed container of gas is halved. Which of the following statements describe what happens to the gas after the decrease in volume?

A container of gas at a pressure of 80 kN/m$$^2$$ has a volume of 0.050 m$$^3$$. What is the pressure when the container expands to a volume of 0.075 m$$^3$$?

force exerted when energy makes an object move

energy transferred when a force makes an object move

Which of the following show a definition of work or a unit of work?

Which of the following show a definition of pressure or a unit of pressure?

Which of the following are equal to 1 kN?

Particles collide with each other more often.

The particles are squashed so they become smaller.

The particles repel each other more strongly all the time.

If the particles in a gas are pushed closer together, the pressure of the gas increases. Which of the following explains why?

A table of weight 500 N stands on the floor. The area of contact between the table and the floor is 200 cm$$^2$$. The pressure exerted by the table on the floor is __________ N/cm$$^2$$.

pressure of gas = force on one inner face of cube ÷ area of one face

pressure of gas = force on one inner face of cube ÷ total area of all faces

The gas exerts pressure because its weight pushes down on the container’s base.

The gas exerts pressure because its particles exert forces on all inner faces.

A sealed container in the shape of a cube contains gas. Which of the following statements are correct?

Explaining pressure changes

Lesson outcome