9 (a) Which metal reacts when added to cold water? A calcium B copper C gold D silver (b) A student investigates the reactivity of four different metals - Edexcel - GCSE Chemistry - Question 9 - 2023 - Paper 1

1. Magnesium

   • Many bubbles produced quickly / bubbles vigorously.
   • Test tube feels hot / warm / warmer than zinc test.

2. Zinc

   • Bubbles produced at a steady rate.
   • Test tube feels slightly warm.

3. Iron

   • No observable reaction.

4. Copper

   • No reaction.

To investigate the gas produced, one should:

1. Apply a lighted splint to the gas (to identify if it is hydrogen).
2. A 'squeaky' pop sound will be heard if hydrogen gas is present.

The balanced chemical equation for the reaction between magnesium and hydrochloric acid is:

$Mg + 2HCl \rightarrow MgCl_2 + H_2$