Particles and their Behaviour
Particles and their behaviour is the topic explaining how the arrangement, movement and spacing of particles determine the properties of solids, liquids and gases. It covers the particle model of the three states of matter, changes of state, diffusion, gas pressure, and density calculations, including finding volume by displacement.
Before you start
No specific prerequisites - this is a good place to start.
Method
- Learn how particle arrangement, movement and spacing differ between solids, liquids and gases.
- Name each change of state (melting, evaporating/boiling, condensing, freezing) and link it to particle behaviour.
- Learn and apply the density equation: density = mass / volume.
- Practise density calculations, including finding the volume of an irregular object by displacement.
- Explain diffusion, gas pressure and compressibility using the particle model.
- Interpret heating and cooling curves, including the flat sections during a change of state.
Worked example
A student measures the mass of an irregularly shaped rock as 156 g. She lowers it into a measuring cylinder containing 80.0 cm3 of water, and the water level rises to 112.0 cm3. Calculate the density of the rock. Give your answer to 3 significant figures.
- Calculate the volume of the rock from the change in water level: 112.0 - 80.0 = 32.0 cm3.
- Write down the density equation: density = mass / volume.
- Substitute the values: density = 156 / 32.0.
- Calculate: 156 / 32.0 = 4.875.
- Round to 3 significant figures: 4.88 g/cm3.
Practice questions
Try each question, then tap to reveal the answer.
Exam-style questions
Written in the style of a KS3 Science exam paper, with a full mark scheme.
Explain, using the particle model, why a gas can be compressed easily but a solid cannot be compressed.
A student records the temperature of melting candle wax every two minutes as it is heated. Time (min): 0, 2, 4, 6, 8, 10, 12; Temperature (degrees C): 20, 35, 48, 48, 48, 60, 72. State the melting point of the wax shown by this data, and explain, in terms of particles, why the temperature stays constant while the wax is melting.
A fixed mass of gas is sealed inside a rigid container and cooled from 80 degrees C to 20 degrees C. State and explain, in terms of particles, what happens to (i) the volume and (ii) the pressure of the gas.
Free printable worksheet
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