POWERPLUSWATERMARKOBJECT3 3 9 ACADEMIC SCIENCE MONARCH PARK COLLEGIATE PARTICLE

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9 Academic Science Monarch Park Collegiate

Particle Theory Of Matter – Introduction

The kinetic theory of matter (particle theory) says that all matter consists of many, very small particles which are constantly moving or in a continual state of motion. The degree to which the particles move is determined by the amount of energy they have and their relationship to other particles. The particles might be atoms, molecules or ions. Use of the general term 'particle' means the precise nature of the particles does not have to be specified.

Particle theory helps to explain properties and behaviour of materials by providing a model which enables us to visualize what is happening on a very small scale inside those materials. As a model it is useful because it appears to explain many phenomena but as with all models it does have limitations.

Solids, liquids and gases

In solids the particles	In liquids the particles	In gases 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	- 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	-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

Fig 1 Particles in solids, liquids and gases

The model can be used to help explain the properties of matter and what happens during physical changes such as melting, boiling and evaporating

The properties of matter

Solids	Liquids	Gases
- have a definite shape and maintain that shape - are difficult to compress as the particles are already packed closely together - are often dense as there are many particles packed closely together	- do not have a definite shape - flow and fill the bottom of a container. They maintain the same volume unless the temperature changes - are difficult to compress because there are quite a lot of particles in a small volume - are often dense because there are quite a lot of particles in a small volume	- do not have a definite shape - expand to fill any container - are easily compressed because there are only a few particles in a large volume - are often low density as there are not many particles in a large space

Particle Theory of Matter S.T.A.M.P.

Spaces between the individual particles are very large compared to the sizes of the particles.

Together close, attract the most.

All particles of the same substance are identical to each other in every way. Different substances are made of different particles.

 

Matter is made up of small microscopic particles.

Particles of matter are always moving.

Changes of State (Phase Changes)

The particles of a solid or liquid possess kinetic energy (energy of motion) and potential energy. The potential energy is due to the force of attraction between the particles. To change the state of a substance, energy must be supplied or removed. For example, energy must be supplied to melt ice; energy must be removed from steam to change it into liquid water. If energy is supplied to a piece of ice which is at zero degrees Celsius it will cause the piece of ice to melt without causing it to change temperature. During this change of state, the energy supplied goes into increasing the total potential energy stored in the bonds between the molecules.

Similarly, during any change of state, it is the potential energy of the particles which changes; the average kinetic energy (and therefore the temperature) remains constant.