Chemical changes: reactivity, acids and electrolysis
Chemical changes questions are about patterns: the reactivity series predicts reactions, and electrolysis rules predict products.
Lesson overview
What you'll learn in this lesson
Carry out quantitative chemistry calculations and explain chemical changes.
Key learning points
- • The reactivity series and extraction
- • Acids, alkalis and titration
- • Electrolysis
This lesson at a glance
- 30 minutes
- 15 parts to scroll through
- 4 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 15
Watch first
Chemical changes: reactivity, acids and electrolysis
An English teaching video on this topic from Brainstorm - Maths and Science. Watch it, then scroll down for the lesson.
In a nutshell
Carry out quantitative chemistry calculations and explain chemical changes.
Learning cycle
Part 2 of 15
Learning cycle 1 of 2
Part 1 · The reactivity series and extraction
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 15
Learn
The reactivity series and extraction
More reactive metals displace less reactive ones from their compounds. Metals more reactive than carbon, such as aluminium, must be extracted by electrolysis, while those below carbon, such as iron, can be reduced with carbon in a furnace. Oxidation is loss of electrons and reduction is gain.
Explore the idea
Part 4 of 15
Learn
Acids, alkalis and titration
Acid + alkali → salt + water; acid + metal → salt + hydrogen; acid + carbonate → salt + water + carbon dioxide. Strong acids ionise completely while weak acids only partly, which is why they differ in pH at the same concentration. Titration finds an unknown concentration using an indicator and concordant results.
Quick check
Part 5 of 15
Quick check
A metal more reactive than carbon must be extracted by
Quick check
Part 6 of 15
Quick check
Oxidation is
Reset break
Part 7 of 15
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.
Learning cycle
Part 8 of 15
Learning cycle 2 of 2
Part 2 · Electrolysis
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 9 of 15
Learn
Electrolysis
In a molten ionic compound, the metal forms at the cathode and the non-metal at the anode. In aqueous solution, hydrogen is produced at the cathode unless the metal is less reactive than hydrogen, and oxygen at the anode unless a halide is present, in which case the halogen forms.
Quick check
Part 10 of 15
Quick check
At the cathode during electrolysis of aqueous sodium chloride you get
Quick check
Part 11 of 15
Quick check
A weak acid differs from a strong acid because it
Explore the idea
Part 12 of 15
Worked example
Worked answer: predict the products of electrolysing aqueous copper chloride, with reasons (4 marks)
At the cathode, copper is less reactive than hydrogen, so copper metal is deposited rather than hydrogen gas (2). At the anode, a halide ion is present, so chlorine gas is produced rather than oxygen (1), and it can be identified because it bleaches damp litmus paper (1). Had the solution been copper sulfate, oxygen would form at the anode instead.
Challenge round
Part 13 of 15
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
Mastery quiz
Part 14 of 15
Marked quiz
End of lesson quiz: Chemical changes: reactivity, acids and electrolysis
4 questions, marked with the reasoning shown. No timer.
1. A metal more reactive than carbon must be extracted by
2. Oxidation is
3. At the cathode during electrolysis of aqueous sodium chloride you get
4. A weak acid differs from a strong acid because it
Lesson round-up
Part 15 of 15
Lesson round-up
Ready when you are
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Luna: 0 out of 4 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 15 · Watch & discover