Acids, alkalis and the pH scale
Acids and alkalis cancel each other out in a reaction called neutralisation — and the pH scale tells you exactly how strong each one is.
Part of your national curriculum
- Chemistry: chemical reactions: Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity
Lesson overview
What you'll learn in this lesson
Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity
Key learning points
- • The pH scale
- • Neutralisation
- • Naming the salt
This lesson at a glance
- 24 minutes
- 16 parts to scroll through
- 3 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 16
Visual introductionPicture this
Acids, alkalis and the pH scale
Acids and alkalis cancel each other out in a reaction called neutralisation — and the pH scale tells you exactly how strong each one is.
In a nutshell
Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity
Learning cycle
Part 2 of 16
Learning cycle 1 of 2
Part 1 · The pH scale
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 16
Learn
The pH scale
The pH scale runs from 0 to 14. Values below 7 are acidic (0 being strongly acidic), 7 is neutral, and values above 7 are alkaline (14 being strongly alkaline). Universal indicator changes colour across this range to show pH.
Reset break
Part 4 of 16
Pause
That's sitting 1 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 16
Learn
Neutralisation
When an acid reacts with an alkali, they neutralise each other, producing a salt and water: acid + alkali → salt + water. For example, hydrochloric acid + sodium hydroxide → sodium chloride + water.
Quick check
Part 6 of 16
Quick check
Part 7 of 16
Reset break
Part 8 of 16
Pause
That's sitting 2 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 16
Learning cycle 2 of 2
Part 2 · Naming the salt
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 16
Learn
Naming the salt
The salt's name depends on the acid and the metal in the alkali. Hydrochloric acid produces 'chloride' salts, sulfuric acid produces 'sulfate' salts, and nitric acid produces 'nitrate' salts, e.g. sodium hydroxide + sulfuric acid → sodium sulfate + water.
Quick check
Part 11 of 16
Reset break
Part 12 of 16
Pause
That's sitting 3 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 13 of 16
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 14 of 16
Game · Recall cards
What pH value is exactly neutral?
Card 1 of 4
Mastery quiz
Part 15 of 16
Marked quiz
End of lesson quiz: Acids, alkalis and the pH scale
4 questions, marked with the reasoning shown. No timer.
1. What pH value is exactly neutral?
2. What are the products of a neutralisation reaction?
3. What salt is formed from sulfuric acid and sodium hydroxide?
4. A pH of 3 indicates
Lesson round-up
Part 16 of 16
Lesson round-up
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Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity