Particles are close together in a regular arrangement
The attraction between particles are strong.
The particles vibrate around a fixed position; a solid has a fixed shape.
The volume does not change because the particles cannot move closer together.
Liquid
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Particles are still close together (most touching) but are arranged irregularly
The force of attraction between particles is less strong than a solid.
The particles move around and slide past each other; liquids can be poured.
Under pressure the volume does not change because the particles cannot move closer together.
Gas
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Particles are far apart, arrangement is random.
The force of attraction between particles is very weak.
The particles move freely and at speed, they collide with each other and bounce away randomly; gasses spread.
Under pressure the gas is pushed into a smaller volume because the particles can move a lot closer together.
Diffusion
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Difussion is where particles mix and spread throughout the space, evening the concentration out until they are the same.
Speed of diffusion
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The smaller the relative molecular mass, the more quickly particles diffuse.
Diffusion is also faster when -
A. It is hotter, the particles move faster as they have more energy
B. It is in gas as the speed of gas particles is faster.
Changing state
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On heating particles gain energy and move faster; they change state when they gain enough energy to overcome the forces of attraction.
On cooling, the particles lose energy and move more slowly; as they get closer the forces of attraction take over and change state.
Cooling and heating curves
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When a substance is pure then the temp remains the same during a change of state (I.e. horizontal part of graph)
During boiling the energy breaks these attractions futher
During melting the energy- heat, is being used to break some of the attractions between particles.
In between state changes the particles are vibrating and moving more as the energy is taken in and the temp rises.
Heating curve
Cooling curve
Purity
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By measuring the melting and boiling points you can tell if pure.
You can identify pure substance by measuring melting and boiling point.
Pure
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Has no particles of any other substance mixed in with it.
Melts and boils at unique temp.
Melts sharply at melting pt
Impure
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Has other particles mixed in
Melts over range temp not sharply.
Melt lower temp
Boil higher temp
Definitions
Element
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Pure substance containing only one type of atom e.g. oxygen
Compound
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A pure substance containing 2 or more types of atom chemically bondede.g. CH4
Mixture
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2 or more substances which are not chemically bonded and can easily be seperated by phisical process. E.g. air