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SavannahYear 8
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ScienceChemical reactions24 min★★ difficulty

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
  • 13 parts to scroll through
  • 3 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

reactionsalkalismeasuringacidityneutralisation

Scroll down — the lesson carries on below

Part 1 of 13 · Discover8%
1

Watch & discover

Part 1 of 13

Watch first

Acids, alkalis and the pH scale

An English teaching video on this topic from Revision Monkey. Watch it, then scroll down for the lesson.

In a nutshell

Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity

2

Learning cycle

Part 2 of 13

Learning cycle 1 of 2

Part 1 · The pH scale

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 13

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.

4

Explore the idea

Part 4 of 13

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.

5

Quick check

Part 5 of 13

Quick check

What pH value is exactly neutral?

6

Reset break

Part 6 of 13

Pause

That's sitting 1 of 2 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.

Stop here for now
7

Quick check

Part 7 of 13

Quick check

What are the products of a neutralisation reaction?

8

Learning cycle

Part 8 of 13

Learning cycle 2 of 2

Part 2 · Naming the salt

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 13

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.

10

Quick check

Part 10 of 13

Quick check

What salt is formed from sulfuric acid and sodium hydroxide?

11

Challenge round

Part 11 of 13

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

12

Mastery quiz

Part 12 of 13

Marked quiz

End of lesson quiz: Acids, alkalis and the pH scale

3 questions, marked with the reasoning shown. No timer.

  1. 1. What pH value is exactly neutral?

  2. 2. What are the products of a neutralisation reaction?

  3. 3. What salt is formed from sulfuric acid and sodium hydroxide?

13

Lesson round-up

Part 13 of 13

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

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Points this lesson

0

Best run

0 in a row

Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 13 · Watch & discover

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    Understand reactions of acids with alkalis to produce a salt plus water, and use the pH scale for measuring acidity

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