Using our Resources

- both air (oxygen) and water are needed for iron to rust

- providing a barrier between iron and any air (oxygen) and water protects the iron from rusting

- sacrificial protection provides protection against rusting, even when the iron is exposed to air and water. The iron needs to be attached to a more reactive metal (zinc, magnesium or aluminium) 

- alloys are harder than pure metals because the regular layers in a pure metal are distorted by differently-sized atoms in an alloy

- copper, gold and aluminium are all alloyed with other metals to make them harder

- pure iron is too soft for it to be very useful

- carefully controlled quantities of carbon and other elements are added to iron to make steel alloys with different properties

- important examples of steels are:

    high carbon steels, which are very hard but brittle

    low carbon steels, which are softer and easily shaped

    stainless steels, which are resistant to corrosion

- monomers affect the properties of the polymers that they produce

- changing reaction conditions can also change the properties of the polymer that is produced

- thermosoftening polymers will soften or melt easily when heated, because their intermolecular forces are relatively weak

- thermosetting polymers will not soften, because of their 'cross-linking', but will eventually char if heated very strongly

- soda glass is made by heating a mixture of sand, limestone and sodium carbonate,

    borosilicate glass is made from sand and boron trioxide, and melts at a higher temperature than soda-lime glass

- clay ceramics include pottery and bricks, they are made by shaping wet clay then heating in a furnace

- composites are usually made of two materials, with one material acting as a binder for the other material, improving a desirable property that neither of the original materials could offer alone

- ammonia is an important chemical for making other products

- ammonia is made from nitrogen and hydrogen in the Haber process

- we carry out the Haber pocess under conditions of about 450°C and 200 atmosphere pressure, using an iron catalyst 

- any unreacted nitrogen and hydrogen are recycled back into the reaction vessel in the Haber process

- the Haber process uses a pressure of around 200 atmospheres to increase the amount of ammonia produced

- although the higher pressures would produce higher yields of ammonia, they would make the chemical plant too expensive to build and run

- a temperature of about 450°C is used for the reaction, although lower temperatures would increase the yield of ammonia, it would be produced too slowly

- ammonia is used to make nitric acid 

- the nitric acid made can then be reacted with more ammonia to make ammonium nitrate fertiliser

- ammonia can also be neutralised by sulfuric acid to make ammonium sulfate fertiliser, and with phosphoric acid to make ammonium phosphate fertiliser

- fertilisers are used to supply nitrogen, phosphorus and potassium to plants, these can all be added to the land at the same time in mixtures of compounds called NPK fertilisers

- the nitrogen comes from ammonia made in the Haber process, which is reacted with acids to make fertilisers such as ammonium nitrate and ammonium sulfate

- the source of phosphorus is phosphate rock, which is mined and then treated with acids to form fertilisers, such as ammonium phosphate and calcium phosphate

- the potassium comes from potassium salts mined from the ground for use as fertilisers, such as potassium chloride and potassium sulfate