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I AM a science teacher and I think anyone who spends time with young children can be one too. It is in the home that children first encounter literature, maths, music and art 鈥� through reading, counting, singing and drawing. But this sort of informal teaching isn鈥檛 so common when it comes to science. That is partly because many people lack the knowledge or confidence to talk about science with children, and partly because science isn鈥檛 ingrained in our culture in quite the same way.

Some children do try out 鈥渆xperiments鈥� at home, such as making a 鈥渧olcano鈥� using bicarbonate of soda, vinegar and washing-up liquid. Mixing bicarb with vinegar results in a chemical reaction that produces carbon dioxide gas. The gas forms bubbles in the washing-up liquid, causing foam to flow out of the container. This delights children but, for me, the real joy is in their realisation that they can make sense of what is happening using the idea that everything is made of atoms and that these can be rearranged, a bit like pieces of Lego.

In this case, I would tell children we are starting with four types of atom 鈥� sodium, carbon, hydrogen and oxygen 鈥� joined together in different ways to make sodium bicarbonate (NaHCO₃) and the molecules of ethanoic acid (CH₃COOH) found in vinegar. When these two chemicals come together, the molecules bump into each other and end up rearranged into new substances: carbon dioxide (CO₂), water (H₂O) and sodium acetate (C₂H₃NaO₂).

Although this reaction is easy to do at home, it isn鈥檛 much of an experiment. Instructions for activities like it are commonplace and tend to consist of directions for recreating entertaining phenomena. However, these guides often miss a key aspect of science: asking questions and trying to find the answers.

Instead of using the bicarbonate of soda and vinegar reaction to make a volcano, you could build a balloon-inflation machine to investigate factors that affect how much gas the reaction produces.

To do this, use a measuring jug to pour 50 millilitres of vinegar into an empty bottle. Then place a funnel into the mouth of a balloon and pour in a level teaspoon of bicarbonate of soda.

Stretch the mouth of the balloon over the open end of the bottle to form an airtight seal, taking care not to let any of the bicarb fall into the vinegar. When you are ready, lift the end of the balloon to mix the reactants.

As you are doing this, try asking questions like 鈥渨hat do you think will happen?鈥�. Perhaps talk about how a solid and liquid are reacting to produce a gas. To turn this activity into an experiment, you could ask 鈥渉ow could we make the balloon even bigger?鈥� You might even investigate what other liquids react with bicarbonate of soda and whether they have anything in common.

What you need

At least 50 ml of vinegar

At least one teaspoon of bicarbonate of soda

A measuring jug

An empty 500 ml plastic drink bottle

A funnel

A balloon

A teaspoon

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