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Test the strength


    Which acids are the strongest? Let’s run a strength competition to find out!

    Ingredients and equipment that you will need

    A leaf of red cabbage
    Lemon juice or orange juice
    Soda crystals (from any supermarket)
    Pipette or straw to use as a dropper

    Method and further information

    Make an indicator with red cabbage juice (see “Make an Indicator“)

    Add a teaspoonful of soda crystals and it turns green. Divide this equally into two jars

    Now add vinegar to one jar using a pipette or with your finger over a straw. Carefully count and record the number of drops until it goes purple.

    Now add lemon or orange juice to the other jar, carefully counting the drops until the colour is exactly the same.

    The acid that needs fewest drops to neutralise it is the stronger. If it takes 10 drops of vinegar and 5 of lemon juice, then the lemon juice must be twice as strong an acid.

    Be careful – you should ask an adult to help you with these experiments. Do your experiments in old yoghurt pots, jam jars or bottle tops. Don’t use cups or glasses in case someone thinks it’s a drink.