1 - PRINCIPLES OF CHEMISTRY

States of matter - 

Solids - 

• strong forces of attraction between particles - close together 
• fixed positions 
• lattice arrangement 
• particles don't move - solids keep definite shape and volume 
• particles vibrate about their positions 
• hotter = more vibration = slight expansion 

Liquids - 

• weak force of attraction between particles 
• randomly arranged 
• free to move past each other 
• generally stay closely together 
• definite volume but not definite shape 
• flow to fill bottom of a container 
• constantly moving with random motion 
• hotter = move faster = slight expansion 

Gases - 

• very weak force of attraction between particles 
• free to move 
• far apart 
• particles travel in straight lines (bounce off objects/each other) 
• no definite shape or volume 
• fill any container 
• move constantly with random motion 
• hotter = move faster = expand/increase pressure 

Changes of state - 

HEAT ENERGY SUPPLIED - 

Solid - Liquid - 

1. Solid heated, particles gain energy 

2. Particles vibrate more, weakens bonds 

3. Expands 

4. Particles gain enough energy to break free from positions 

MELTING 

5. Liquid

Liquid - Gas - 

1. Liquid heated, particles gain more energy 

2. Particles move faster, weakens and breaks bonds holding it together 

3. Particles gain enough energy to break bonds 

EVAPORATING 

4. Gas 

HEAT ENERGY GIVEN OUT - 

Opposite happens! 

Gas - liquid - 

CONDENSING 

Liquid - solid - 

FREEZING