Every card in Acids and alkalis, Year 8: more practice
The whole deck, in order — so you can read it through before your child ever sees it.
- Put these in order from the most acidic to the most alkaline: bleach (pH 12), lemon juice (pH 2), water (pH 7).
Lemon juice, water, bleach
HintThe lower the pH number, the more acidic the substance.
WhyAcids have a pH below 7, neutral is exactly 7, and alkalis are above 7. The further from 7, the stronger the acid or alkali.
- The pH scale used in school runs from 0 up to which number? (number only)
14
HintThe middle of the scale, 7, is neutral.
WhyThe pH scale runs from 0, strongly acidic, to 14, strongly alkaline, with 7 as neutral. It measures how acidic or alkaline a solution is.
- Hydrochloric acid is mixed with sodium hydroxide until neither is left over. What is produced?
Sodium chloride and water
HintThe salt is named from the metal in the alkali and the acid used; a familiar liquid forms too.
WhyHydrochloric acid makes chlorides, so the salt is sodium chloride. This is table salt, though the word salt in chemistry covers many compounds.
- Sodium hydroxide solution is added a little at a time to hydrochloric acid. What happens to the pH of the mixture?
It rises towards 7
HintThe alkali is gradually cancelling out the acid.
WhyAs alkali is added the acid is used up, so the pH goes up. At the exact balance point the mixture is neutral at pH 7, and more alkali pushes it above 7.
- Indigestion tablets contain a substance that reacts with excess stomach acid. What type of reaction takes place?
Neutralisation
HintThe tablet cancels out the acid rather than just covering it up.
WhyThe tablets contain a base, such as magnesium hydroxide, which reacts with the extra hydrochloric acid and brings its strength down towards neutral.
- Which method gives a more precise pH reading: universal indicator against a colour chart, or a pH probe?
A pH probe
HintOne method depends on your eye matching a colour; the other gives a number on a screen.
WhyA pH probe reads a value, often to one decimal place. Matching colours by eye is quick and cheap but can be a judgement call.
- Why should you rinse a pH probe in distilled water between one solution and the next?
So that the last solution does not contaminate the next reading
HintThink about what is still on the probe after it has been in the first liquid.
WhyLeft-over liquid on the probe would mix into the next solution and shift its reading. Rinsing makes each reading fair and repeatable.
- What happens to a lit splint held at the mouth of a test tube of hydrogen?
It goes out with a squeaky pop
HintHydrogen burns very quickly, using oxygen from the air in the tube.
WhyThe squeaky pop is the small explosion of hydrogen burning with oxygen. It is the standard test for hydrogen gas.
- Zinc reacts with hydrochloric acid. Name the salt that is formed (two words).
Zinc chloride
HintName the metal first, then use the ending that matches the acid.
WhyZinc + hydrochloric acid → zinc chloride + hydrogen. Hydrochloric acid always makes chlorides.
- Magnesium and iron are each added to the same dilute hydrochloric acid. Which fizzes more quickly, and why?
Magnesium, because it is more reactive
HintA metal higher up the reactivity series reacts eagerly.
WhyMagnesium sits above iron in the reactivity series, so it reacts faster and gives off hydrogen more vigorously.
1★ KS3-CHEM-ACD-0035
2★ KS3-CHEM-ACD-0036
3★ KS3-CHEM-ACD-0037
4★ KS3-CHEM-ACD-0038
5★ KS3-CHEM-ACD-0039
6★ KS3-CHEM-ACD-0040
7★ KS3-CHEM-ACD-0041
8★ KS3-CHEM-ACD-0042
9★ KS3-CHEM-ACD-0043
10★ KS3-CHEM-ACD-0044
Keep what you learn
Here, nothing is saved. In your child’s own sky every card is scheduled — it comes back just before they’d forget it — and the professor who wrote it is one tap away.