Particles and states of matter
Clear notes with worked examples, then 4 practice questions with answers. Written by Beyond Tutors tutors for the KS3 National Curriculum.
The particle model
Everything is made of tiny particles. How they are arranged decides the state.
SOLID: particles touching, in a regular pattern, vibrate on the spot. Fixed shape, cannot be squashed.
LIQUID: particles touching but arranged randomly, can slide past each other. Flows, takes the shape of its container, cannot be squashed.
GAS: particles far apart, moving quickly in all directions. Fills its container, can be squashed.
Changes of state
solid → liquid: melting
liquid → gas: boiling / evaporating
gas → liquid: condensing
liquid → solid: freezing
solid → gas: subliming
Diffusion
Particles spread out from where there are lots to where there are few. It is faster in gases and when hotter.
Mixtures
- Filtration: separates an insoluble solid from a liquid (sand and water)
- Evaporation: gets a dissolved solid back (salt from salty water)
- Chromatography: separates coloured dyes in ink
Practice questions
Try each one, then tap to see the answer and why.
- Question 1 · Changes of state
What is the change from gas to liquid called?
- AMelting
- BEvaporating
- CCondensing
- DFreezing
Show the answer
C: Condensing
Gas to liquid is condensing, e.g. water droplets forming on a cold window.
- Question 2 · Changes of state
Ice melts at 0°C. What happens to the particles as the ice melts?
- AThey get bigger
- BThey gain energy and break out of their fixed positions
- CThey stop moving
- DThey turn into new particles
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B: They gain energy and break out of their fixed positions
Heat gives the particles energy; they break free of the fixed pattern and can move past each other.
- Question 3 · Changes of state
What is the difference between evaporation and boiling?
- AThere is no difference
- BEvaporation happens only at the surface, at any temperature below boiling point
- CBoiling happens only at the surface
- DEvaporation only happens to solids
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B: Evaporation happens only at the surface, at any temperature below boiling point
Evaporation happens at the surface at any temperature; boiling happens throughout the liquid at its boiling point.
- Question 4 · States of matter
Which statement about liquids is true?
- AThey have a fixed shape
- BTheir particles are far apart
- CThey can be easily squashed
- DThey take the shape of their container
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D: They take the shape of their container
Liquid particles touch but can slide past each other, so liquids flow and take their container's shape.