1Metals and acids
Many metals react with dilute acids. They fizz because hydrogen gas is made: metal + acid → salt + hydrogen.
hydrogensalt
Lesson 14.4 notes
Making salts
Acids with metals, metal oxides and carbonates, the tests for hydrogen and carbon dioxide, naming salts and growing crystals.
2The squeaky pop
To test for hydrogen, hold a lit splint at the mouth of the tube. Hydrogen burns with a squeaky pop.
squeaky pop
3Not every metal reacts
The more reactive the metal, the faster it fizzes. Copper is too unreactive to react with dilute hydrochloric or sulfuric acid.
reactivity
4Carbonates and acids
Carbonates fizz with acids, giving off carbon dioxide, which turns limewater milky: carbonate + acid → salt + water + carbon dioxide.
carbonatecarbon dioxide
5Metal oxides and acids
Metal oxides are bases. copper oxide + sulfuric acid → copper sulfate + water. The blue colour is the copper sulfate.
metal oxide
6Naming salts
The metal comes first, then a part from the acid: hydrochloric acid makes chlorides, sulfuric acid sulfates and nitric acid nitrates.
chloridesulfatenitrate
7Growing crystals
Add copper oxide to warm acid until it is in excess (some is left over). Filter off the extra, evaporate some water, then leave to cool: blue crystals grow.
excesscrystallisation
Explore: Salt maker
Choose an acid and something to add. Watch what happens, test the gas and name the salt.
Common mistake: A salt is not just table salt
In chemistry a salt is any compound made when the hydrogen in an acid is replaced by a metal. Table salt, sodium chloride, is one salt; copper sulfate and magnesium chloride are salts too.
Remember
- metal + acid → salt + hydrogen. Hydrogen burns with a squeaky pop.
- metal oxide + acid → salt + water. metal carbonate + acid → salt + water + carbon dioxide.
- Hydrochloric acid makes chlorides, sulfuric acid makes sulfates and nitric acid makes nitrates.
Going further at GCSE