Acids and bases
The pH scale measures how acidic or alkaline a substance is. Substances with a pH of 7 are neutral, substances with a pH greater than 7 are alkaline (or 'basic') and substances with a pH lower than 7 are acidic. Alkalis are 'bases' that are soluble in water. (All alkalis are bases but not all bases are alkalis.)
The chemical properties of many solutions enable them to be divided into three categories – acids, alkalis and neutral solutions. The strength of the acidity or alkalinity is expressed by the pH scale.
Solutions with a pH of 7 are neutral.
Solutions with a pH greater than 7 are alkaline. The higher the pH, the stronger the alkali.
Solutions with a pH less than 7 are acidic. The lower the pH, the stronger the acid.
If universal indicator is added to a solution it changes to a colour that shows the pH of the solution.
Here are some examples of acids, alkalis and their pH values.
|strong alkali||14||drain cleaner|
|10||milk of magnesia|
|strong acid||0||battery acid|
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