1 of 10© boardworks ltd 2013 acids and alkalis

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Acids and Alkalis

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What are acids and alkalis?

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What are indicators?

Indicators are chemicals that change colour in the presence of an acid or an alkali.

There are many different indicators. Many of them come from plants, like red cabbage. Different indicators turn different colours.

Universal indicator is a mixture of indicators. It is useful because it shows a range of colours from pH 1–14.

Geranium plants grown in acidic soil have redder flowers, while geraniums grown in alkali soil have bluer flowers.

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What does the pH scale show?

The pH scale runs from 1 to 14. The numbers 1 to 6 represent acidic conditions and 8 to 14 represent alkali conditions. A pH value 7 is neutral.

1 2 3 4 5 6 7 8 9 10 11 12 13 14

What are the pH values of some everyday items?

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What does the pH scale show?

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What is the order of pH?

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What are bases?

Bases are substances that react with acids. All alkalis are bases.

The oxides, hydroxides and carbonates of metals, such as sodium hydroxide, are bases.

Ammonia is a base that does not contain a metal.

Alkalis are bases that are soluble in water.

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Acids and bases – true or false?

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pH change during neutralization