Chemistry

Forces between molecules determine the properties of plastics

Strong covalent bonds hold the atoms together in long chains. But it's the bonds between the different molecule chains that determine the properties of the plastic. - thermosoftning polymers- weak force

Thermosetting polymers- strong forces

The reaction conditions - temperature- will affect the properties of a polymer.

The rate of reaction depends on 4 things

• temperature
• concentration
• catalyst
• surface area of solids

3 different ways the rate of reaction can be measured

• precipitation
• change in mass
• the volume of gas given off

More collisions increase the rate of reaction
1) a higher temperature, because the particles move quicker, therefore collide more often
2) higher concentration, increasing the pressure,, which means the particles are more squashed together therefore collide more
3) larger surface area, more surface area to work on, frequent collisions

Catalysts speed up reactions
A catalyst is a substance which speeds up a reaction without being changed or used up in the reaction

Exothermic reaction is one which transfers energy to the surroundings usually in the form of heat and usually in the form of heat and usually shown by a rise in temperature.
E.g burning fuels

ENDOTHERMIC reaction is one which takes in energy from the surroundings usually in the form if heat and is usually shown by a fall in temperature.

The strongest acid has a ph 0, the strongest has a ph 14

And indicator is just a dye that changes colour

Acids and bases neutralise each other

Acid is a substance with a ph less than 7

A base is a substance with a ph greater than 7

An alkali is a base that dissolves in water.

The reaction between acids and bases is called neutralisation, acid+base Salt+water

Acids reacting with metals-

Metals react wi acids to make salts

Hydrochloric acid will always produce chloride salts

Sulfuric acid will always produce sulfate salts

Nitric acid produces nitrate salts when neutralised

Oxides, hydroxides and ammonia

Metal oxides and metal hydroxides are bases

All metal oxides and metal hydroxides react with acids to form a salt and water

Electrolysis means splitting up with electricity

If you pass an electric current through an ionic substance that's molten or in solution, it breaks down into the elements it's made of.

Electrolytes(liquid to conduct electricity) contains free ions.

For an electrical circuit to be complete, there's got to be a flow of electrons

Electrolysis reactions involve oxidation and reduction
Oxidation is loss, reeducation is gain

When common salt is dissolved in water and electrolysed it produces 3 useful products hydrogen, chloride, sodium hydroxide