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
- 14 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 14
Watch first
Chemical reactions and equations
An English teaching video on this topic from Revision Monkey. 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
Learning cycle
Part 2 of 14
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 14
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.
Explore the idea
Part 4 of 14
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 5 of 14
Quick check
What happens to atoms during a chemical reaction?
Reset break
Part 6 of 14
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.
Quick check
Part 7 of 14
Quick check
In 2Mg + O2 → 2MgO, how many magnesium atoms are on each side?
Learning cycle
Part 8 of 14
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 9 of 14
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 10 of 14
Quick check
Why must chemical equations be balanced?
Challenge round
Part 11 of 14
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 12 of 14
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.
Mastery quiz
Part 13 of 14
Marked quiz
End of lesson quiz: Chemical reactions and equations
3 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?
Lesson round-up
Part 14 of 14
Lesson round-up
Ready when you are
Quiz score
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Points this lesson
0
Best run
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Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo 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.
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
- Name the variable the club changed the second time, and one variable they kept the same.
- Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
- Write a conclusion for the club's report, saying how far the evidence supports it.
Method and results
WritingWrite 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
WritingExplain 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
DiagramDraw the apparatus or the process in pencil, label it fully, and photograph it.
1 labelled diagram
Reading and notes
ReadingRead 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 14 · Watch & discover
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Understand chemical reactions as the rearrangement of atoms, represented by word and symbol equations