What is left when the liquid dries up?
In a lab, a teacher can let the liquid from the reacted aluminium dry up. A white solid is left. Compare it with the metal. The metal was shiny. The white solid is not shiny. The metal made bubbles with the acid. The white solid does not make bubbles when acid is added again. So the metal has changed into a new substance with different properties. The metal did not just disappear, and it did not hide: its parts are still there, but joined in a new way. A new substance means a material that behaves differently. We can also see a safe change at home. A grown-up puts a dull coin in a cup with vinegar and a pinch of salt. After some time, the coin looks brighter, because the dull coating reacts and goes into the liquid.
| Property | Aluminium metal | White solid left |
|---|---|---|
| looks | shiny | dull white |
| bubbles with acid | yes | no |
| kind of substance | metal | new substance |
Coin clean-up. With a grown-up, stand a dull copper-coloured coin in a cup with a little vinegar and a pinch of salt, on a tray. Check after thirty minutes and after a few hours. Rinse the coin well and wash your hands afterwards. Do not taste the liquid. Never put metal into strong cleaners.