Resource 3: Neutralisation Circus
Background information / subject knowledge for teacher
Suggested stations – instructions for the teacher
- Universal indicator – acid, 10 ml measuring cylinder, beaker, universal indicator, spatula or teaspoon, baking soda, stick or glass rod.
- Insect stings – a beaker of acid labeled ‘insect sting’, test-tubes in a rack, universal indicator, three beakers labeled ‘remedy 1’ (containing baking soda), ‘remedy 2’ (containing vinegar or lemon juice) and ‘remedy 3’ (containing sugar), spatulas or teaspoons.
- Indigestion – two different types of indigestion (anti-acid) tablet, mortar and pestle (or spoon and plate), two beakers (one containing acid), methyl orange indicator, teat pipette, glass rod or stick to stir.
- Neutralisation – a bottle of acid and a bottle of alkali or approximately the same strength, beaker, 10 ml measuring cylinder, universal indicator, teat pipette, stirring rod.
- Lemon juice – several lemons, baking powder, teaspoon, the names of the chemicals involved on separate pieces of paper or card, some ‘+’ and ‘→‘ signs and a piece of paper with some word equations written out (just the reactants) for the students to complete.
- Acidic soil – some soil mixed with citric acid (or any solid acid), spatulas or teaspoons, 10 ml measuring cylinder, test-tubes in a rack, filter funnel, beaker, filter paper, universal indicator, fertiliser 1 (containing sugar), fertiliser 2 (containing lime), fertiliser 3 (containing solid citric acid).
- Mix and match – pieces of card or paper with the numbers 1–14, 14 pieces of paper with the names of colours written on them (or coloured paper if you can get it), 14 pieces of paper with a ranges of substances written on whose pH you hope the students will know – water, hydrochloric acid, sodium hydroxide, lime, lemon juice, etc.
Suggested stations – instructions for the students
- Universal indicator – Pour 10 ml of acid provided into a beaker and add three drops of universal indicator. Add baking soda, half a spatula at a time. Stir after each addition. Record the colours that you see and explain what is happening. When the colour does not change any more, add a few drops of acid. Keep going until it goes back to the original colour. Rinse out the beaker ready for the next group.
- Insect stings – Transfer 1 ml of ‘insect sting’ into a test-tube. Add universal indicator. Add one of the suggested remedies and note the colour change. Repeat until you have tried all the remedies and decide which ones would be suitable to use to remove the ‘sting’.
- Indigestion – Crush an anti-acid tablet and transfer it to a beaker with a few drops of indicator. Add acid, a little at a time, until the indicator remains red. Repeat for a different type of tablet. Which tablet neutralises the most acid?
- Neutralisation – Your task is to find out exactly how much alkali is needed to neutralise 10ml of the acid. Measure out 10 ml of acid, add some indicator and add the alkali very slowly. If you have time, do it twice and take an average of your results. At the end you will compare your results with the rest of the class.
- Lemon juice – Wash your hands. Dip your finger in some lemon juice and put it in your mouth, so that your mouth has an acid taste. Lick your finger and dip it into some baking powder. Place your finger on your tongue. What do you taste? Can you explain what has happened? Arrange the words provided to make a word equation for the reaction. If you have time, try some more word equations.
- Acidic soil – Place 1 spatula of soil in a test tube, add 10ml of water. Place your finger on the end and shake the tube. Filter the solution, or let it settle and pour off the liquid. Add a few drops of universal indicator. Divide the solution between three tubes and add one spatula of fertiliser to each one. Which fertiliser would be best for neutralising the soil?
- Mix and match – Place the numbers of the pH scale in order on your desk. For each number, add a colour and an example of a substance with that pH. Check your answers. Which ones did you get right?