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Acids, bases and salts - (CCEA)Acids, bases and salts

Many chemicals are acidic, neutral or alkaline. We can distinguish one from another using indicators. Acidity and alkalinity are measured on the pH scale. A salt is formed when an acid is neutralised by an alkali.

Part of Chemistry (Single Science)Structures, trends, chemical reactions, quantitative chemistry and analysis

Acids, bases and salts

Indicators

An is a chemical that changes colour in , and solutions. Some common indicators include red litmus paper, blue litmus paper, phenolphthalein, and methyl orange.

IndicatorAcidicNeutralAlkaline
Red litmus paperredredblue
Blue litmus paperredblueblue
Phenolphthaleincolourlesscolourlesspink
Methyl orangeredorangeyellow
IndicatorRed litmus paper
Acidicred
Neutralred
Alkalineblue
IndicatorBlue litmus paper
Acidicred
Neutralblue
Alkalineblue
IndicatorPhenolphthalein
Acidiccolourless
Neutralcolourless
Alkalinepink
IndicatorMethyl orange
Acidicred
Neutralorange
Alkalineyellow
Blue litmus paper is dipped in a beaker of acid and turns red.
Image caption,
Blue litmus paper changes to red in acids
Red litmus paper changes to blue in alkalis.
Image caption,
Red litmus paper changes to blue in alkalis