Interconversions between the three states of matter
4 marks · NormalThe diagram below shows a substance being heated until it completely changes from solid to gas.
State the name of the process occurring as the solid changes directly to a gas.
Describe what happens to the arrangement and movement of the particles during this process.
Name the reverse process (gas to solid) and give one example of a substance that sublimates.
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(a) Sublimation
(b) Particles change from being closely packed and vibrating in fixed positions (solid) to being far apart and moving rapidly in all directions (gas).
(c) Deposition (or de-sublimation); examples: iodine, dry ice (solid carbon dioxide), or naphthalene.
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Marking points
B1 (a) · 1 mark · Correctly states 'sublimation'.
B2 (b) · 1 mark · Describes particles as closely packed/vibrating in fixed positions (solid) and far apart/moving freely (gas).
B3 (b) · 1 mark · States particles move rapidly and randomly in a gas.
B4 (c) · 1 mark · Names 'deposition' or equivalent as reverse, with suitable example (e.g. iodine, dry ice, naphthalene).
Worked solution
a) The process is called sublimation.
b) In sublimation, particles in a solid, which are closely packed and only vibrate at fixed positions, gain enough energy to break free and become far apart, moving rapidly and randomly as a gas.
c) The reverse process is deposition (or de-sublimation). An example of a substance that sublimates is dry ice (solid carbon dioxide) or iodine.