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
- 19 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
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Part 1 of 19
Visual introductionPicture this
Chemical changes: reactivity, acids and electrolysis
Chemical changes questions are about patterns: the reactivity series predicts reactions, and electrolysis rules predict products.
In a nutshell
Carry out quantitative chemistry calculations and explain chemical changes.
Learning cycle
Part 2 of 19
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.
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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.
Reset break
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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
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Quick check
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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.
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Part 9 of 19
Learning cycle 2 of 2
Part 2 · Electrolysis
A short piece of teaching, then a check to make sure it has landed.
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Part 10 of 19
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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
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Part 12 of 19
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Quick check
Part 13 of 19
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Part 14 of 19
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 15 of 19
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
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Part 16 of 19
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Challenge round
Part 17 of 19
Game · Recall cards
A metal more reactive than carbon must be extracted by
Card 1 of 4
Mastery quiz
Part 18 of 19
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
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