Heating things up is really important in chemistry. But in the early days of the science, this wasn’t easy. Fire was probably a pile of dirty wood or sooty coal in a grate. So pioneer chemists like Joseph Priestley and Anton Lavoisier used nice clean sunshine... and a lens. Not a little one like you keep in your pocket. No, these ‘burning glasses’ were huge, 30cm or more. Lavoisier even had a monster lens 2.5m in diameter. Here is how to make your own great big burning glass – out of water.
As well as water, you’ll need cling-film and a ring, ideally a bit smaller than the cling-film. The wheel-rim from a child’s bike will do nicely, or even a full-size bike wheel-rim. You’ll also need a mirror as wide as the ring and twice as long.
Cover the ring in cling film, trying to make the sheet flat. You can put a piece of elastic – or a chain of elastic bands – around a wheel-rim over...