Changes of State

IGCSE Edexcel Chemistry
1.2 Interconversions between states of matter
Key Concept: State changes involve energy transfer and changes in particle arrangement and movement.

Section A: Naming Changes

1. Name the change of state for each process. [4]

a) Solid to liquid

b) Liquid to gas

c) Gas to liquid

d) Solid to gas

2. Which changes of state are endothermic? [2]

Section B: Particle Model

3. Explain what happens to particle energy during melting. [2]
4. Explain why boiling happens at a fixed temperature for a pure substance. [2]

Total marks: 10

Mark Scheme

1. a) Melting b) Boiling/evaporation c) Condensation d) Sublimation [4]
2. Melting, boiling/evaporation, sublimation [2]
3. Energy is absorbed; particles gain kinetic energy and overcome attractions [2]
4. Energy goes into breaking intermolecular forces; temperature stays constant until change complete [2]