Acids, salts, and neutralisation

Science · Matter & Materials · ages 12-13

Name ______________________ Date ____________

How do you test for hydrogen gas?
- Bubble it through limewater: it turns cloudy
- Hold a lit splint near it: it burns with a squeaky pop
- Test it with damp litmus paper
What gas is produced when an acid reacts with a metal?
- Oxygen
- Hydrogen
- Carbon dioxide
Neutralisation happens when an acid reacts with an alkali.
Circle one: True False
Hydrochloric acid reacts with the metal oxide copper oxide. Which products form?
- Copper chloride and water
- Copper chloride and hydrogen
- Copper sulfate and water
Hydrochloric acid reacts with sodium hydroxide. What salt forms?
- Sodium sulfate
- Sodium nitrate
- Sodium chloride
Which of these is an example of neutralisation being used?
- Adding sand to loosen the soil
- Treating acidic soil with lime
- Watering the soil more often
Nitric acid reacts with potassium hydroxide. What salt forms?
- Potassium nitrate
- Potassium chloride
- Potassium sulfate
A student writes: 'acid + metal oxide → salt + hydrogen'. What is the mistake?
- It should make salt + oxygen, not hydrogen
- There is no mistake
- It should make salt + water, not hydrogen

Answer key

For grown-ups. Fold this page away before handing over the rest.

Hold a lit splint near it: it burns with a squeaky pop · A squeaky pop with a lit splint means hydrogen is present. The limewater test is for carbon dioxide instead.
Hydrogen · Acid + metal always makes a salt and hydrogen gas.
True · The acid and alkali cancel each other out and form a salt and water.
Copper chloride and water · A metal oxide reacts with an acid the way an alkali does: it makes a salt and water, never hydrogen. The salt's metal is copper and hydrochloric acid gives the chloride part, so the salt is copper chloride.
Sodium chloride · Hydrochloric acid always gives a 'chloride' salt, and the metal comes from sodium hydroxide, so together you get sodium chloride.
Treating acidic soil with lime · Lime is an alkali. It neutralises the acid in the soil, forming a salt.
Potassium nitrate · Nitric acid always gives a 'nitrate' salt, and the metal comes from potassium hydroxide, so you get potassium nitrate.
It should make salt + water, not hydrogen · Hydrogen only forms when an acid reacts with a metal. A metal oxide reacts with acid to make salt and water.