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Metals with Water and Steam

IGCSE 0620 · CBSE Class 10 · Reactivity series
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Water trough

Cold water · 22 °C
Water temp22.0 °C
Rate of fizzingNothing yet
pH of solution7.0
H2 given off0 cm³
Metal left0.100 g
Nothing on the bench yet Pick a metal, then drop it in. Every one of them behaves the way it really does. The ones that float, float. The ones that melt, melt. And the ones that do nothing, do nothing.

The sample

0.100 g piece
Equation
Pick a metal
Where it sits in the reactivity series

Quick quiz

0 of 10 answered

What this experiment shows

How violently a metal reacts with water is one of the clearest ways to put metals in order of reactivity. Potassium, sodium and calcium react with cold water; magnesium barely does, but reacts readily with steam; zinc and iron need steam; copper does not react at all. The pattern is the point - the higher a metal is in the reactivity series, the more easily it loses electrons and forms positive ions.

2Na + 2H2O → 2NaOH + H2

What you need

  • A trough of cold water, and universal indicator
  • Small, freshly cut pieces of the metals
  • For steam: damp mineral wool in a boiling tube, with the metal further along
  • A safety screen, tongs and eye protection

How it is done

  1. For cold water, drop a small piece of the metal onto the water and watch from behind a screen.
  2. Test the solution afterwards with indicator.
  3. For steam, put damp mineral wool at the closed end of a tube and the metal in the middle.
  4. Heat the metal, then heat the wool so steam passes over it.
  5. Collect the gas at the open end and test it with a lit splint.

What you should see

  • Potassium: violent, lilac flame, the metal melts and skates about.
  • Sodium: rapid, melts to a ball, fizzes across the surface.
  • Calcium: steady fizzing, sinks then rises as bubbles cling to it.
  • Magnesium: very slow in cold water, vigorous with steam giving magnesium oxide.
  • The solution turns purple with universal indicator, because a hydroxide has formed.

Where marks are lost

  • Writing the product of a metal with steam as a hydroxide. Steam gives the oxide plus hydrogen.
  • Saying the gas "pops" without saying that a squeaky pop identifies hydrogen.
  • Confusing reactivity with how shiny or how hard a metal is.
  • Using a piece of sodium bigger than a grain of rice.

Questions students ask

Why does the solution turn purple?
A metal hydroxide has dissolved in the water, making the solution alkaline. Universal indicator goes purple in strong alkali.
Why does magnesium react with steam but not cold water?
Steam is much hotter, so the particles have far more energy. That is enough to get a reaction going that cold water cannot start at any useful rate.
Which gas is given off?
Hydrogen, in every case. Test it by holding a lit splint at the mouth of the tube: it burns with a squeaky pop.

Try these next

Written for Cambridge IGCSE Chemistry 0620 and CBSE Class 9-12 by Ajay Shekhawat, founder of MrChemCoach. Run the simulator above, then check yourself against the questions.