Five Tests That Sort Everything
- HARD, and it has a lustre, meaning it shines
- Gets hot when heated, and carries electricity too
- FLATTENS when hammered, instead of shattering
- RINGS when struck. Tap a steel plate, then tap a plastic one
Presenter notes: Open with two objects and a question they cannot answer yet. Hold up a gold ring, or a photograph of one, and a rusty iron nail. Say that both metals have been in the ground for the whole history of the Earth, and ask why one of them comes out of a river bed still shining while the other has to be dragged out of a rock with fire and then painted every year to stop it disappearing. Nobody will have the answer, and by the end of the period they will, because there is one idea underneath it. Then promise the smaller prize as well: they will find out why the sheets on their own roof, which everybody calls zinc sheets, are actually iron.