Warning: The lithium hydroxide produced when lithium reacts with water is caustic. Do not contact. Only the lithium and the calcium cannot be recovered unharmed form the water.
You will need:
One or more of these: lithium, calcium, magnesium, aluminium, zinc, iron, nickel, tin, lead, copper, silver, gold
Lots of test tubes
For consistency, all of the metals should be about the same shape and size. Zinc powder will react more vigorously than an aluminium chunk, even though aluminium is higher on the reactivity series.
There is a series called the reactivity series. It ranks the metals from most reactive to least reactive. The most reactive elements react with water, oxidizing acids, and nonoxidizing acids. They are isolated by electrolysis. The second group reacts with oxidizing and nonoxidizing acids. They can be isolated by a carbon reduction. The third group reacts only with oxidizing acids. They are very easy to isolate. The list of metals above is ranked in the order of the activity series.
Add warm water to all of the test tubes. Add the metals, starting with gold. Gold and silver have absolutely no reaction. Copper and lead very slowly corrode because of the dissolved oxygen in the water (not because of the water), both forming a protective layer that inhibits further corrosion. Tin and nickel do not react. Iron and zinc corrode a little more readily, although zinc forms a partially protective layer. This is still corrosion by the dissolved oxygen, not by the water itself. Aluminium has a tough protective layer, making it completely unreactive. Magnesium has a protective layer not as strong as aluminium. Since magnesium is so high on the reactivity series, it is corroded by water itself, not by the dissolved oxygen in water. Small hydrogen bubbles can be seen escaping from the magnesium. Calcium forms an incomplete protective layer, but still reacts quite vigorously with water. Lithium, the highest on the reactivity series, forms no protective layer and (if it is not covered in oil) reacts instantly and vigorously with water.
The nature of the oxide (crumbly or adhesive) affects the reactivity of the metal as well as its placement on the reactivity series. The oxide layer can be removed by treatment with hydrochloric acid and the true reactivity of the metal can be seen.