1. The Particle Theory of Matter

2. The Particle Theory
1. Matter is made up of tiny particles (Atoms, Molecules or Ions)
2. Particles of Matter are in constant motion.
3. Particles of Matter are held together by very strong electric forces
4. There are empty spaces between the particles of matter that are very large compared to the particles themselves.
5. Each substance has unique particles that are different from the particles of other substances
6. Temperature affects the speed of the particles.  The higher the temperature, the faster the speed of the particles.

3. Why is it important
The particle theory can help us explain many physical and chemical properties of matter.
Pure substances are homogeneous – this is because there is only one type of particle present in the substance . Thus, they all behave the same way

4. …states of matter… Solids: The particles…
are held tightly and packed fairly close together - they are strongly attracted to each other
are in fixed positions but they do vibrate

5. …states of matter… Liquids The particles…
are fairly close together with some attraction between them
are able to move around in all directions but movement is limited by attractions between particles

6. …states of matter… Gases The particles…
have little attraction between them
are free to move in all directions and collide with each other and with the walls of a container and are widely spaced out

7. Can we use the particle theory to explain some of the properties of matter?
Why does a liquid take the shape of a container but a solid doesn’t?
Why do you think that the same volume of different materials have differing masses
ie) 1cm3 of gold weighs 19.3g but 1cm3 of aluminum weighs 2.7g

8. Why does this happen?

9. What about physical changes?
No new materials are formed and the particles do not change apart from gaining or losing energy

10. What about Chemical changes?
During chemical changes particles do change with atoms or ions regrouping .
Bonds (links) between atoms break and new ones form and energy is either given out or taken in.

11. Changes of State Evaporating
Within a liquid some particles have more energy than other. These "more energetic particles" may have enough energy to escape from the surface of the liquid as gas
Evaporation happens from the surface of the liquid
Evaporation is assisted by windy conditions which help to remove the vapor particles from the liquid so that more escape

12. Boiling
If a liquid is heated the particles are given more energy and move faster and faster expanding the liquid.
The most energetic particles at the surface escape from the surface of the liquid as a vapor as it gets warmer
The particles need energy to overcome the attractions between them
Eventually even particles in the middle of the liquid form bubbles of gas in the liquid
The particles in the gas are the same as they were in the liquid they just have more energy.

13. Boiling…
As these particles cool down and lose energy they will condense and turn back to liquid
Fun fact: the "steam" coming out of a boiling kettle can only be seen because some of the gas particles have condensed to form small droplets of water.

14. Melting
When a solid is heated the particles gain energy and start to vibrate faster and faster
Initially the structure is gradually weakened which has the effect of expanding the solid
Further heating provides more energy until the particles start to break free of the structure
The particles in the liquid are the same as in the solid but they have more energy

15. Freezing and Condensation
When a gas turns to a liquid (condenses) or a liquid turns to a solid (solidifies) the particles lose energy to the surroundings

16. What about Dissolving?
If a solid dissolves, in mixing its particles break apart and form a loose association with the liquid (solvent) particles.
A solid will not dissolve in a liquid if its particles are unable to form links to the liquid particles.
This is why some substances are soluble and some aren’t…it depends on the molecules in the substance

17. What about Dissolving?

18. Changes of State