Properties of the different states of matter
4 marks · NormalThe diagrams below show the arrangement of particles in three different states of matter.
Identify which numbered group of circles (1, 2 or 3) represents a gas.
State two differences between the arrangement and movement of the particles in a solid and those in a gas.
Explain why solids are not easily compressed.
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(a) 3
(b) — · must show solids: closely packed, fixed positions, vibrate, gases: far apart, random motion, no fixed shape
(c) Particles are tightly packed together in solids so there is little space to compress them.
Common mistakes: Mixing up particle diagrams; Vague answers about arrangement
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Marking points
A1 (a) · 1 mark · Correctly identifies group 3 as representing a gas.
B1 (b) · 1 mark · States one valid difference in arrangement or movement between solid and gas.
B2 (b) · 1 mark · States a second valid difference in arrangement or movement.
C1 (c) · 1 mark · Explains that solids are not easily compressed because particles are packed tightly together.
Worked solution
a) Group 3 shows the particles widely spaced, which is the arrangement for a gas.
b) In solids, particles are tightly packed in a regular arrangement and only vibrate about fixed positions. In gases, particles are far apart, have no fixed positions, and move randomly and rapidly in all directions.
c) Solids cannot be compressed easily because their particles are already tightly packed together, leaving little space for further compression.