Displacement Reactions

Lesson Overview

Subject: Science
Level: AQA GCSE Foundation (UK)
Topic: Chemical Changes – Displacement Reactions
Class Size: 18 students
Lesson Duration: 1 hour

This engaging and hands-on lesson will introduce students to displacement reactions, helping them understand how more reactive metals can replace less reactive metals from compounds. The session will involve practical demonstrations, collaborative discussions, and structured questions aligned with the AQA GCSE Foundation Science curriculum.

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Curriculum Alignment

AQA GCSE Foundation Science – Chemical Changes

• Chemical Reactions: Understand how different metals react with metal compounds.
• Reactivity Series: Recognise how the reactivity of metals determines displacement reactions.
• Balanced Equations: Develop the ability to represent simple reactions with word and symbol equations.

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Lesson Objectives

By the end of the lesson, students will:

1. Understand what a displacement reaction is.
2. Identify the role of the reactivity series in predicting displacement reactions.
3. Observe and analyse a real chemical displacement reaction.
4. Write word and symbol equations for displacement reactions.
5. Apply knowledge to predict the outcomes of similar reactions.

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Lesson Structure

Starter Activity (10 minutes) – Reactivity Puzzle

• Display a mystery box containing different metals (magnesium, iron, zinc, copper).
• Ask students: Which of these metals do you think would react most strongly in a reaction?
• Facilitate a brief discussion linking this to prior knowledge of metals and reactivity.
• Introduce the idea that some metals can displace others due to their position in the reactivity series.

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Main Activity (30 minutes) – Practical Demonstration & Student Experiment

Demonstration: Copper Sulphate & Iron Reaction (10 minutes)

• Display a test tube containing blue copper(II) sulphate solution.
• Ask: What do you think will happen if I add iron nails to this solution?
• Add iron nails to the copper sulphate solution and observe over 2–3 minutes.
• Guide students to notice the change:
  • The solution loses its blue colour as copper is displaced.
  • A reddish-brown copper deposit forms on the iron nail.
  • The iron slowly dissolves into the solution to form iron sulphate.

Student Experiment: Zinc & Copper Sulphate (20 minutes)

Students will work in pairs and conduct a simple displacement reaction.

Equipment:

• Test tubes
• Copper(II) sulphate solution
• Zinc granules
• Tweezers
• Observation sheets

Instructions:

1. Pour copper(II) sulphate solution into a test tube (half full).
2. Add a small piece of zinc metal using tweezers.
3. Observe changes over 5 minutes:
   • Solution fades in colour.
   • A dark solid (copper) appears.
4. Record observations in a structured grid.

Key Question:

• Why does zinc cause the reaction, but copper alone wouldn’t react back?
• How does this relate to the Reactivity Series?

Students will complete a sentence starter:
"Zinc is more reactive than copper, so it displaces copper from copper sulphate solution. This forms..."

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Developing Understanding (15 minutes) – Equation Challenge

• Introduce the word equation:
  Zinc + Copper Sulphate → Zinc Sulphate + Copper
• Ask students to balance and write the symbol equation:
  Zn + CuSO₄ → ZnSO₄ + Cu
• Give students 2 additional examples to attempt using their knowledge.

Extension:

• Challenge students to predict and explain what would happen if magnesium was used instead of zinc.

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Plenary (5 minutes) – Exit Ticket: "One Thing I Learned"

• Ask each student to write down one new thing they learned today on a post-it note.
• Gather responses and use a quick ‘pass the ball’ game where students share their points aloud.
• Conclude by linking displacement reactions to real-world applications (e.g., extracting metals, batteries).

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Assessment Opportunities

• Formative:
  • Participation in the starter discussion.
  • Observations recorded during the practical task.
  • Sentence starter completion during the explanation phase.
• Summative:
  • Correctly writing and balancing (word & symbol) displacement equations.
  • Verbal responses during plenary session.

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Differentiation Strategies

• For Support Learners:
  • Provide structured sentence starters and equation templates.
  • Use visual step-by-step guides for the experiment.
• For Higher Ability Students:
  • Ask them to predict whether certain reactions will occur using the reactivity series.
  • Introduce half-equations to explain electron transfer in the displacement process.

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Resources Required

1. Copper(II) sulphate solution
2. Iron nails
3. Zinc granules
4. Test tubes
5. Tweezers
6. Observation sheets
7. Reactivity series chart

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Teacher Reflection Questions

• Did students engage with the practical activity?
• Were students able to accurately predict and explain what happened in the experiment?
• Did students demonstrate an understanding of how reactivity impacts displacement reactions?
• What could be improved for next time?

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Next Steps/Homework (Optional)

• Research another example of a displacement reaction in everyday life.
• Find out how displacement reactions are used in industry (e.g., metal extraction).

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Final Thought for Students:

"Remember, chemistry is all about patterns! If you understand the reactivity series, you can predict how metals will behave in different reactions."

This lesson ensures active learning with hands-on experimentation and logical reasoning, offering a memorable and practical approach to displacement reactions! 🎉