1. Matter:
The Particle Theory

2. What is the Particle Theory?
Means of representing the behaviour of matter
Imagine solids, liquids and gases to be made up of microscopic particles

3. solid Particles arranged in regular way
Strong forces holding them together
Can’t move out of position
Can vibrate about position

4. liquid Particles in contact & can slide over each other
Weaker forces holding them together
No regular arrangement of particles
Takes up the shape of the container

5. gas Particles much farther apart from each other
Very weak forces between gas particles
Complete freedom of movement & move quickly
Particles take up all available space

6. PARTICLE THEORY
Qualities
Limitations

7. Changes of State Melting Evaporating Solid Gas Liquid Condensing
Freezing
Energy

8. Change of State – Melting Point
Solid is heated – heat energy causes particles to vibrate
Heating continues – particles move faster & faster
Break free from fixed position – begin to slide over each other
The temperature at which the solid melts – melting point

9. Melting Point Particles vibrate more Vibrating a little
Solid melted to form solid

10. Change of State – Boiling Point
Liquid heated – particles get more energy & move faster & faster
Eventually ALL particles have enough energy to overcome forces
Particles break away from liquid and form a gas
Particles escaping quickly causes bubbles of gas forming inside the liquid (water vapour in case of water) – boiling point

11. Change of State – Boiling Point
Particles have enough energy to escape
Particles in liquid state
Particles move faster

12. Sublimation
Some substances when heated change directly from solid to gas – sublimation
Example: carbon dioxide (dry ice)
Reverse: gas to solid - deposition

13. Change of State
When gas cooled: particles slow down, get closer to each other, liquid formed eventually = CONDENSATION
When liquids cooled: particles slow down even more, get even closer together, solid formed eventually = FUSION/FREEZING

14. Condensation

15. Fusion