AQA GCSE Combined Science: Physics: Particle Model of Matter

Water can exist as a solid (ice), a liquid (water) and a gas (water vapour). The particle model can be used to explain the differences between these three states.

Describe the arrangement and movement of the particles in a solid, a liquid and a gas, and explain, in terms of the particles, why a gas can be compressed much more easily than a solid or a liquid. (6 marks)

A student measured the density of a small irregular stone (a required practical). The stone was placed on a balance and then lowered on a thread into a measuring cylinder containing water, and the rise in the water level was recorded. The results are shown below.

Measurement	Value
Mass of stone	84 g
Volume of water before adding stone	50 cm³
Volume of water after adding stone	80 cm³

(a) Determine the volume of the stone, in cm³. (1 mark)

(b) Calculate the density of the stone, in g/cm³. Use $\rho = \dfrac{m}{V}$ρ=Vm​. Show your working and give the unit. (3 marks)

A block of ice at its melting point of 0 °C is being melted into water at 0 °C. The specific latent heat of fusion of ice is 334 000 J/kg.

(a) Calculate the energy needed to melt 0.50 kg of ice at 0 °C into water at 0 °C. Use $E = mL$E=mL. Show your working and give the unit. (2 marks)

(b) While the ice is melting, energy is being supplied but the temperature stays at 0 °C. State what is happening to this energy at the particle level. (1 mark)

A copper block of mass 0.40 kg is heated. The specific heat capacity of copper is 385 J/kg °C.

(a) Calculate the energy needed to raise the temperature of the block by 25 °C. Use $E = mc\Delta\theta$E=mcΔθ. Show your working and give the unit. (2 marks)

(b) The same amount of energy is supplied to a block of a different metal of the same mass, but its temperature rises by more than 25 °C. State what this tells you about the specific heat capacity of the second metal compared with copper. (1 mark)

A fixed mass of gas is sealed inside a rigid container. The gas exerts a pressure on the walls of the container.

Explain, in terms of the motion of the particles, how the gas produces a pressure on the walls of the container. (2 marks)

When a substance changes state, for example when ice melts into water, the total mass of the substance does not change.

State the name given to a physical change, such as melting or boiling, in which no new substance is made and the change can be reversed. (1 mark)