Acid plus metal: making a salt and hydrogen
Chemistry · Key Stage 3 · The School
The general pattern
Metal + acid → salt + hydrogen. Magnesium + hydrochloric acid → magnesium chloride + hydrogen. Zinc + sulfuric acid → zinc sulfate + hydrogen. The salt's name follows the same rule as always: the metal gives its first name, the acid gives its surname. The gas is always hydrogen, whichever metal and acid you use.
Testing for the gas
Hold a lit splint at the mouth of the test tube. Hydrogen burns with a distinctive SQUEAKY POP. This is the standard chemical test for hydrogen gas, and it is worth learning exactly, because "it made a sound" is not specific enough to count as identifying the gas.
Not every metal reacts
How vigorously a metal reacts with acid follows the REACTIVITY SERIES. Very reactive metals like magnesium fizz strongly. Less reactive metals like iron react slowly. Metals below hydrogen in the series, such as copper, do not react with dilute acid at all — no gas, no fizzing, nothing observable happens.
Magnesium in dilute hydrochloric acid: magnesium is high in the reactivity series, so expect strong fizzing and a squeaky pop from the hydrogen produced. Iron filings in the same acid: iron is less reactive, so expect a slower, gentler fizz. Copper turnings in the same acid: copper is below hydrogen in the series, so predict correctly that nothing observable happens at all. Testing all three confirms exactly this pattern — reactivity predicted the outcome before a single test tube was touched.