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NPK fertilisers

These contain nitrogen, phosphorous and potassium

Formulations of various salts containing appropriate percentages of the elements.

Fertiliser examples

Potassium chloride, potassium sulfate and phosphate rock are obtained by mining

Phosphate rock needs to be treated with an acid to produce a soluble salt which is then used as a fertiliser. Ammonia can be used to manufacture ammonium salts and nitric acid.

The Haber process

Used to manufacture ammonia

Ammonia is used to produce fertilisers

Nitrogen + hydrogen ammonia

Raw materials

Nitrogen from the air while hydrogen from natural gas

Both of these gases are purified before being passed over an iron catalyst. This is completed under high temperature (about 450⁰C) and pressure (about 200 atmospheres).

Catalyst

Iron

The catalyst speeds up both directions of the reaction, therefore not actually increasing the amount of valuable product.

Composite materials

A mixture of materials put together for a specific purpose e.g. strength

Soda-lime glass, made by heating sand, sodium carbonate and limestone.

Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than

soda-lime glass.

MDF wood (woodchips, shavings, sawdust and resin)

Concrete (cement, sand and gravel)

Ceramic materials

Made from clay

Made by shaping wet clay and then heating in a furnace, common examples include pottery and bricks.

Polymers

Many monomers can make polymers

These factors affect the properties of the polymer. Low density (LD) polymers and high density (HD) polymers are produced from ethene. These are formed under different conditions.

Corrosion

The destruction of materials by chemical reactions with substances in the environment

An example of this is iron rusting; iron reacts with oxygen from the air to form iron oxide (rust) water needs to be present for iron to rust.

Preventing corrosion

Coatings can be added to metals to act as a barrier

Examples of this are greasing, painting and electroplating. Aluminium has an oxide coating that protects the metal from further corrosion.

Sacrificial corrosion

When a more reactive metal is used to coat a less reactive metal

This means that the coating will react with the air and not the underlying metal. An example of this is zinc used to galvanise iron.

The Haber process – conditions and equilibrium

Pressure

The reactants side of the equation has more molecules of gas. This means that if pressure is increased, equilibrium shifts towards the production of ammonia (Le Chatelier’s principle). The pressure needs to be as high as possible.

Temperature

The forward reaction is exothermic. Decreasing temperature increases ammonia production at equilibrium. The exothermic reaction that occurs releases energy to surrounding, opposing the temperature decreases. Too low though and collisions would be too infrequent to be financially viable.

Polymers

Thermosetting

polymers that do not melt when they are heated.

Thermosoftening

polymers that melt when they are heated.

Phosphate rock

Treatment

Products

Nitric acid

The acid is neutralised with ammonia to produce ammonium phosphate, a NPK fertiliser.

Sulfuric acid

Calcium phosphate and calcium sulfate (a single superphosphate).

Phosphoric acid

Calcium phosphate (a triple superphosphate).

Alloys

A mixture of two elements, one of which must be a metal e.g. Bronze is an alloy of

copper and tin and Brass is an alloy of copper and zinc.

Gold carats

Gold jewellery is usually an alloy with silver, copper and zinc. The carat of the jewellery is a measure of the amount of gold in it e.g. 18 carat is 75% gold, 24 carat is 100% gold.

Steels

Alloys of iron, carbon and other metals.

High carbon steel is strong but brittle.

Low carbon steel is softer and easily shaped.

Steel containing chromium and nickel (stainless) are hard and corrosion resistant.

Aluminium alloys are low density.