unit 2 AQA chemistry

What is a base?

Bases

Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide are bases.

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What is an acid?

Bases

Substances that can react with acids and neutralise them to make a salt and water are called bases. They are usually metal oxides or metal hydroxides. For example, copper oxide and sodium hydroxide are bases.

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What is an alkali?

Alkalis

Bases that dissolve in water are called alkalis. Copper oxide is not an alkali because it does not dissolve in water. Sodium hydroxide is an alkali because it does dissolve in water.

Alkaline solutions have a pH of more than 7. The stronger the alkali, the higher the pH number. Alkalis turn red litmus paper blue. They turn universal indicator paper dark blue or purple if they are strongly alkaline, and blue-green if they are weakly alkaline.

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What are neutral solutions?

Neutral solutions

Neutral solutions have a pH of 7. They do not change the colour of litmus paper, but they turn universal indicator paper green. Water is neutral.

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