Science lesson plan · 10th grade (Year 11 in England) · 45 minutes
Predict the products of electrolysis
Chemical reactions, acids and bases
CCSS NGSS.HS-PS1-2England: GCSE Combined Science: Chemical changes (electrolysis)
Objective and success criteria
Students will: Predict the products of electrolysis.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Build ionic formulae from ion charges; The reactivity series and displacement
Leads to: Oxidation, reduction and half-equations
Materials: Teacher demo or video, Indicator color chart, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Build ionic formulae from ion charges; The reactivity series and displacement). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What is the formula of lithium sulfide? (Ions: Li⁺ and S²⁻) (Li₂S / Li₂S₂ / Li₃S / LiS) → Li₂SPrompt: The total positive charge must equal the total negative charge.
- In Al₂(CO₃)₃ (aluminium carbonate), how many aluminium ions are there for each formula unit? → 2Prompt: Look at the small number after the symbol or bracket.
- What is the formula of aluminium nitrate? (Ions: Al³⁺ and NO₃⁻) (Al(NO₃)₄ / AlNO₃₃ / Al₃NO₃ / Al(NO₃)₃) → Al(NO₃)₃Prompt: The total positive charge must equal the total negative charge.
Hook · 5 min
- Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
- Share the objective: Predict the products of electrolysis. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Electrolysis of copper(II) chloride solution: what forms at the cathode (negative electrode)?
- Step 1: Solution: compare the metal with hydrogen in the reactivity series.
- Step 2: So the answer is: copper
- Answer: copper
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Electrolysis of molten sodium chloride: what forms at the cathode (negative electrode)? (sodium / lead / hydrogen / aluminium) → sodiumPrompt: Positive ions are attracted to the negative cathode.
- Electrolysis of copper(II) chloride solution: what forms at the anode (positive electrode)? (oxygen / hydrogen / bromine / chlorine) → chlorinePrompt: Negative ions are attracted to the positive anode.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Why is extracting aluminium by electrolysis so expensive? (Aluminium is less reactive than carbon / Aluminium ore is very rare / It needs huge amounts of electricity to melt the ore and drive the reaction / The electrodes are made of gold) → It needs huge amounts of electricity to melt the ore and drive the reactionPrompt: Cryolite lowers the melting point, but a lot of energy is still needed.
- Electrolysis of copper(II) sulfate solution: what forms at the cathode (negative electrode)? (oxygen / lead / copper / zinc) → copperPrompt: Positive ions are attracted to the negative cathode.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Build ionic formulae from ion charges.
- Use concrete materials: teacher demo or video.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Oxidation, reduction and half-equations.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-10.
Free lesson plan from eurekami.com/lesson-plan-builder