The Particle Theory of Matter

The Particle Theory1. 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.

Why is it importantThe 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

…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

…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

…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

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

Why does this happen?

What about physical changes? No new materials are formed and the

particles do not change apart from gaining or losing energy

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.

Changes of State

EvaporatingWithin 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

BoilingIf 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.

Boiling…As these particles cool down and lose energy

they will condense and turn back to liquidFun 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.

MeltingWhen a solid is heated the particles gain

energy and start to vibrate faster and fasterInitially the structure is gradually weakened

which has the effect of expanding the solidFurther 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

Freezing and CondensationWhen a gas turns to a liquid (condenses) or a

liquid turns to a solid (solidifies) the particles lose energy to the surroundings

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.

What about Dissolving?

Changes of State