Chemical reactions and equations
In every chemical reaction, atoms are never created or destroyed — they are simply rearranged into new substances.
Part of your national curriculum
- Chemistry: chemical reactions: Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations
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
- • Reactants become products
- • Word and symbol equations
- • Why equations must balance
This lesson at a glance
- 26 minutes
- 17 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 17
Visual introductionPicture this
Chemical reactions and equations
In every chemical reaction, atoms are never created or destroyed — they are simply rearranged into new substances.
In a nutshell
Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations
Learning cycle
Part 2 of 17
Learning cycle 1 of 2
Part 1 · Reactants become products
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 17
Learn
Reactants become products
In a chemical reaction, reactants are converted into products with different properties. For example, magnesium reacts with oxygen to form magnesium oxide: magnesium + oxygen → magnesium oxide. The atoms are rearranged, not lost.
Reset break
Part 4 of 17
Pause
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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 17
Learn
Word and symbol equations
A word equation names the substances involved. A symbol equation uses chemical formulae and must be balanced, so the same number of each type of atom appears on both sides: 2Mg + O2 → 2MgO shows conservation of atoms.
Quick check
Part 6 of 17
Quick check
Part 7 of 17
Reset break
Part 8 of 17
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 17
Learning cycle 2 of 2
Part 2 · Why equations must balance
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 17
Learn
Why equations must balance
Because atoms cannot be created or destroyed in a chemical reaction, the total mass of reactants equals the total mass of products. Balancing equations is simply a way of showing this conservation of atoms clearly.
Quick check
Part 11 of 17
Reset break
Part 12 of 17
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 17
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 17
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
In a ____ reaction, reactants are converted into products with different properties.
A ____ equation uses chemical formulae and must be balanced, so the same number of each type of atom appears on both sides: 2Mg + O2 → 2MgO shows conservation of atoms.
Challenge round
Part 15 of 17
Game · Recall cards
What happens to atoms during a chemical reaction?
Card 1 of 4
Mastery quiz
Part 16 of 17
Marked quiz
End of lesson quiz: Chemical reactions and equations
4 questions, marked with the reasoning shown. No timer.
1. What happens to atoms during a chemical reaction?
2. In 2Mg + O2 → 2MgO, how many magnesium atoms are on each side?
3. Why must chemical equations be balanced?
4. Balancing an equation means changing
Lesson round-up
Part 17 of 17
Lesson round-up
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Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations