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SavannahYear 8
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ScienceChemistry foundations for GCSE (AQA 8462)30 min★★★ difficulty

Balancing equations and the reactivity series

Atoms are never created or destroyed in a reaction — only rearranged. Balancing is simply making the page agree with that fact.

Lesson overview

What you'll learn in this lesson

Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations

Key learning points

  • • Conservation of mass
  • • A reliable balancing method
  • • The reactivity series
  • • Displacement and extraction

This lesson at a glance

  • 30 minutes
  • 18 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

chemicalreactionsrearrangementrepresentedsymbol

Scroll down — the lesson carries on below

Part 1 of 18 · Discover6%
1

Watch & discover

Part 1 of 18

Watch first

Balancing equations and the reactivity series

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

In a nutshell

Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations

2

What you already know

Part 2 of 18

Before we start

What you already know

You should already know how to read chemical formulae and that mass is conserved in reactions.

3

Key words

Part 3 of 18

Key words

Words you'll need today

Reactant
A substance you start with.
Product
A substance made.
Balanced equation
One with equal numbers of each atom on both sides.
Displacement
A more reactive metal taking the place of a less reactive one.
Reactivity series
Metals ordered by how readily they react.
4

Learning cycle

Part 4 of 18

Learning cycle 1 of 2

Balancing without guesswork

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

5

Explore the idea

Part 5 of 18

Learn

Conservation of mass

The same atoms exist before and after; they have swapped partners. If a reaction appears to lose mass, a gas has escaped; if it appears to gain, a gas from the air has joined in. Nothing has vanished.

6

Explore the idea

Part 6 of 18

Learn

A reliable balancing method

Never change a subscript — that would change the substance. Only put big numbers in front. Count each element, balance metals first, then non-metals, then hydrogen, then oxygen last. Recount at the end: CH4 + 2O2 → CO2 + 2H2O.

7

Quick check

Part 7 of 18

Quick check

Balance: __CH4 + __O2 → CO2 + __H2O

8

Reset break

Part 8 of 18

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
9

Quick check

Part 9 of 18

Quick check

To balance you may change only...

10

Learning cycle

Part 10 of 18

Learning cycle 2 of 2

Predicting with the reactivity series

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

11

Explore the idea

Part 11 of 18

Learn

The reactivity series

Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, copper, silver, gold. Reactivity reflects how readily a metal loses electrons, which is why the top of the list reacts violently with water and the bottom is found as the metal itself.

12

Explore the idea

Part 12 of 18

Learn

Displacement and extraction

A more reactive metal displaces a less reactive one from its compound: zinc + copper sulfate → zinc sulfate + copper, and the blue solution fades. The same logic explains extraction: metals below carbon can be reduced with carbon, while those above need electrolysis.

13

Quick check

Part 13 of 18

Quick check

Which displacement happens?

14

Quick check

Part 14 of 18

Quick check

Metals above carbon are extracted by...

15

Common mix-ups

Part 15 of 18

Common mix-ups

Things people often get wrong

  • Changing a subscript to balance an equation changes the chemical itself.
  • Mass appearing to change usually means a gas entered or escaped.
  • Gold's rarity is not why it is unreactive — its position in the series is.
16

Challenge round

Part 16 of 18

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

17

Mastery quiz

Part 17 of 18

Marked quiz

End of lesson quiz: Balancing equations and the reactivity series

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

  1. 1. Mass is conserved because atoms are...

  2. 2. Balance oxygen...

  3. 3. Most reactive listed here:

  4. 4. A fading blue solution suggests...

  5. 5. Iron is extracted using...

  6. 6. Gold is found as the metal because it is...

18

Lesson round-up

Part 18 of 18

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 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 18 · Watch & discover

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