States of Matter

IGCSE Edexcel Chemistry
1.1 Particle model of solids, liquids and gases
Key Concept: The arrangement, movement and energy of particles explain the properties of solids, liquids and gases.

Section A: Particle Model

1. Describe the arrangement and movement of particles in a solid. [2]
2. Describe the arrangement and movement of particles in a gas. [2]
3. Which state has the highest particle energy? Explain briefly. [2]

Section B: Properties

4. Explain why a liquid can flow but a solid cannot. [2]
5. Explain why gases are compressible but solids are not. [2]

Total marks: 10

Mark Scheme

1. Particles closely packed in fixed positions; vibrate about fixed points [2]
2. Particles far apart; move rapidly and randomly in all directions [2]
3. Gas; particles have the most kinetic energy/fastest movement [2]
4. Liquid particles can slide past each other; solid particles are fixed in a lattice [2]
5. Gases have large gaps that can be squeezed; solids have little space between particles [2]