Page 96 - Science Coursebook

7.1 What is a salt?

When you think about salt you probably think of the salt you put in your food, as a
flavouring. This is sodium chloride. But there are many other kinds of salts, for example,

copper sulfate, potassium nitrate and calcium carbonate.
Many salts have important uses in everyday life. The photographs show some examples.

Calcium sulfate is a salt that is In sport you can use magnesium Aluminium sulfate is added to
used to make blackboard chalk. carbonate to keep your hands dyes to help them to stick to
dry, so they do not slip. fibres.

Ammonium nitrate is used as a Copper sulfate is used to stop Sodium chloride is used to
fertiliser to help crops grow well. fungi growing on these soya preserve food and, as table salt,
seeds when they are planted. to flavour food.
Acids and salts
Every day, the chemical industry makes hundreds of thousands of
tonnes of different salts. Many methods for making salts start

with acids.
All acids contain hydrogen. The table below gives the formulae of the
three common acids that you find in the laboratory. The table also

shows some examples of the salts that can be formed from these acids.
Two other acids that you may meet are carbonic acid and citric
acid. Carbonic acid is a weak acid that is formed when carbon
dioxide reacts with water. Salts made from carbonic acid are called
carbonates.

Citric acid is found in citrus fruits, such as oranges and lemons. Salts Bottles of laboratory acid.
formed using citric acid are called citrates.

Name of acid Formula Salts formed from the acid Example of salt Formula of salt
hydrochloric acid HCl chlorides sodium chloride NaCl
sulfuric acid H SO 4 sulfates copper sulfate CuSO 4
2
nitric acid HNO 3 nitrates potassium nitrate KNO 3

94 7 Salts

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