2.5 States of matter and the particle model
6 exam questions worth 11 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which change of state is sublimation?
Choose one answer.
Correct Not quite: the answer is Solid to gas
Mark scheme
C
Model answer
C: sublimation is a solid turning straight into a gas.
Describe the arrangement and movement of the particles in a liquid.
Mark scheme
- random arrangement (1)
- particles close together / touching (1)
- particles move around each other (1)
Model answer
The particles are arranged randomly but are still touching, and they can move around each other.
Substance X melts at −7 °C and boils at 59 °C.
What is the state of X at 25 °C? Explain your answer.
Mark scheme
- liquid (1)
- 25 °C is above the melting point but below the boiling point (1)
Model answer
X is a liquid, because 25 °C is between its melting point (−7 °C) and its boiling point (59 °C).
Explain what happens to the particles when a solid melts.
Mark scheme
- particles gain energy (1)
- forces between the particles are overcome, so particles can move around each other (1)
Model answer
Energy is transferred to the particles. They vibrate more until the forces holding them in fixed positions are overcome, and they can move around each other.
Give two limitations of the simple particle model.
Mark scheme
any two from:
- particles shown as solid spheres (1)
- no forces shown between particles (1)
- all particles shown the same size / shape (1)
- does not show the movement of the particles (1)
Model answer
The model shows particles as solid spheres, and it does not show the forces between them.
Give the state symbol for sodium chloride dissolved in water.
Mark scheme
- (aq) (1)
Model answer
(aq), meaning aqueous.
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