The Expanding Cap

The Expanding Cap

You will need: Food jar and cap.

Have you ever seen your mother struggling to unscrew the metal cap of a jar that refuses to budge? Often, because of the partial vacuum in the jar, and the sticky nature of the contents, caps become quite difficult to remove.

Perhaps you will be able to help.

You have proved that metal is a good conductor of heat, much better than glass. Therefore, if you can contrive to warm the metal cap it should expand more than the jar - and this expansion should be sufficient to enable you to unscrew the cap.

You can either turn the jar upside down in a saucepan and pour about half an inch of hot water into the container, or you can hold the metal cap under a stream of hot water from the faucet for a minute.

You will discover that this will indeed enable you to remove the cap from the jar. Another example of science being put to practical use!

Children learn best through doing

Before children can understand a thing, they need experience: seeing, touching, hearing, tasting, smelling; choosing, arranging, putting things together, taking things apart. Experimenting with real things.

Old-time school teaching used only words and the teachers thought children knew something if they could repeat it. Now we know better. To reach practical understanding we do not need to use many words with young children.

Children are clever. They learn a lot, without being taught. The greatest skill - to be able to talk, to communicate is learnt outside school. In the classroom it's the children who need to talk the most. Unfortunately it is the teacher who does most of the talking!