Thursday, 02 July
key stage 3
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Lots of everyday substances contains acids or alkalis:
Acids are found in:
Rainwater is a little acidic, but pollution (e.g. sulphur dioxide) from burning fossil fuels may make it even more acidic, forming acid rain.
When acids are present in food, they usually taste sour (think of the taste of lemon juice or vinegar). Strong acids are very dangerous.
Alkalis are found in:
Notice the connection between these substances? Alkalis are often found in substances for cleaning.
Strong alkali substances are just as dangerous as strong acidic substances, causing very serious burns if they come into contact with your skin.
When an acid is added to an alkali or an alkali added to an acid, neutralisation takes place: the substance changes pH to become closer to being neutral.
Neutralisation is sometimes very useful. For example, if your stomach makes too much acid, then you may suffer from stomach ache. Taking Alka-Seltzer (an antacid) will neutralise this extra acid and relieve the pain.
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