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Science lesson plan · 9th grade (Year 10 in England) · 60 minutes

Balancing chemical equations

Chemical reactions, acids and bases

CCSS NGSS.MS-PS1-5CCSS NGSS.HS-PS1-7England: KS4 Combined Science: Chemical changes

Objective and success criteria

Students will: Balancing chemical equations.

  • 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: Reactants, products and word equations

Leads to: Moles and reacting masses

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 · 6 min

  • Quick retrieval from earlier learning (Reactants, products and word equations). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Complete the word equation: zinc + oxygen → ___ (carbon dioxide / zinc oxide / zinc carbonate / iron oxide) → zinc oxidePrompt: A metal reacting with oxygen makes a metal oxide.
  2. What is needed for fuels to burn? (water and light / oxygen and enough heat / nitrogen only / carbon dioxide) → oxygen and enough heatPrompt: Think of the fire triangle: fuel, heat and…
  3. Word equations: which statement is NOT true? (Thermal decomposition breaks a substance down using heat. / Incomplete combustion can produce carbon monoxide, a poisonous gas. / Combustion is a reaction with oxygen. / Products are the substances you start with.) → Products are the substances you start with.Prompt: Which side of the arrow is which?

Hook · 6 min

  • Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
  • Share the objective: Balancing chemical equations. Read the success criteria together.

I do: model it · 12 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Balance the equation. What number goes in the gap? __Al + 3Clâ‚‚ → 2AlCl₃
  • Step 1: 2Al + 3Clâ‚‚ → 2AlCl₃
  • Step 2: Al: 2 on the left, 2 on the right.
  • Step 3: So the answer is: 2
  • Answer: 2
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 12 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Balance the equation. What number goes in the gap? 2Mg + O₂ → __MgO → 2Prompt: Count the Mg atoms on each side.
  2. Zn + 2HCl → ZnCl₂ + H₂ How many Cl atoms are on the left side of this balanced equation? → 2Prompt: Multiply the big number in front by the small number after the symbol.

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Which equation is correctly balanced? (2H₂O₂ → 2H₂O + 2O₂ / H₂O₂ → 2H₂O + O₂ / 2H₂O₂ → 3H₂O + O₂ / 2H₂O₂ → 2H₂O + O₂) → 2H₂O₂ → 2H₂O + O₂Prompt: Count each type of atom on both sides.
  2. Balance the equation. What number goes in the gap? __Mg + O₂ → 2MgO → 2Prompt: Count the Mg atoms on each side.

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: Reactants, products and word equations.
  • 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: Moles and reacting masses.
  • 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-9.

Free lesson plan from eurekami.com/lesson-plan-builder

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Balancing chemical equations

Name

Date

Score/ 8

  1. Question 1

    Zn + 2HCl → ZnCl₂ + H₂ How many Cl atoms are on the right side of this balanced equation?

    Answer

  2. Question 2

    Which equation is correctly balanced?

    • A. C₃H₈ + 5Oâ‚‚ → 3COâ‚‚ + 4Hâ‚‚O
    • B. C₃H₈ + 5Oâ‚‚ → 4COâ‚‚ + 4Hâ‚‚O
    • C. 2C₃H₈ + 5Oâ‚‚ → 3COâ‚‚ + 4Hâ‚‚O
    • D. C₃H₈ + 5Oâ‚‚ → 3COâ‚‚ + 3Hâ‚‚O

  3. Question 3

    Balance the equation. What number goes in the gap? __Na + Cl₂ → 2NaCl

    Answer

  4. Question 4

    N₂ + 3H₂ → 2NH₃ How many N atoms are on the right side of this balanced equation?

    Answer

  5. Question 5

    Balance the equation. What number goes in the gap? __H₂ + O₂ → 2H₂O

    Answer

  6. Question 6

    2K + 2H₂O → 2KOH + H₂ How many K atoms are on the right side of this balanced equation?

    Answer

  7. Question 7

    Balance the equation. What number goes in the gap? C₃H₈ + 5O₂ → __CO₂ + 4H₂O

    Answer

  8. Question 8

    2H₂ + O₂ → 2H₂O How many O atoms are on the right side of this balanced equation?

    Answer

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Answer key: Balancing chemical equations

  1. 1. 2

  2. 2. A. C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

  3. 3. 2

  4. 4. 2

  5. 5. 2

  6. 6. 2

  7. 7. 3

  8. 8. 2