1. LO: to be able to explain the uses of salt, where it comes from and the methods needed to get it Salt

2. Salt was used to preserve meat and fish when appliances were not invented to keep them fresh. It is also used to flavour the food. It is used for salting roads and as a source of chemicals for chlorine.

3. Salt has been extracted from the Essex coast for 2000 years. This is because rainfall here is lower and this causes the concentration of salt in the estuaries/rivers is higher. Therefore less fuel is needed to evaporate the water and separate the salt.

4. There are two underground mines in England (North Yorkshire and Winsford, Cheshire). This salt is used on roads in freezing weather. Adding salt means the ice and snow melts, this because salty water has a lower freezing point than pure water.. The rock contains 90% sodium chloride in the form of halite. The halite is mixed with insoluble impurities (reddish clay).

5. The salt used for the chemical industry in Britain is not mined, it is extracted by pumping water down into the rock. The salt dissolves and is carried to the surface in solution. The impurities do not dissolve and stay in the ground. The solution of salt in water is called brine.

6. Salt crystal are recovered from the brine by evaporating the water. On such a large scale, the evaporates have to be efficient as possible to minimise the energy needed to turn water into steam. The salt crystallises as the water evaporates. The crystals are separated from the remaining brine by filtering or using a centrifuge. 1)Name the solvent and the solute in brine. 2)Outline how you would make some pure salt from rock salt on a small scale on a laboratory.

7. Large-scale pumping of brine in Cheshire started in 1870. uncontrolled pumping for 60 years created very large underground holes. This led to subsidence and flooding of land. Pumping is planned so that the holes in rock are spaced out and separated by pillars of rock.

8. LO: to be able to explain the uses of salt, where it comes from and the methods needed to get it Review Learning: