Science lesson plan · 11th grade (Year 12 in England) · 30 minutes

Moles and reacting masses

Chemical reactions, acids and bases

CCSS NGSS.HS-PS1-7England: KS4 Combined Science: Chemical changes (quantitative chemistry, Higher)

Objective and success criteria

Students will: Moles and reacting masses.

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: Balancing chemical equations

Leads to: Count particles with the Avogadro constant; Volumes of gases from moles (24 dm³ at RTP); Concentration in mol/dm³

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 · 4 min

Quick retrieval from earlier learning (Balancing chemical equations). Students answer on mini whiteboards.
Show answers together and note who needs support in the main task.

Balance the equation. What number goes in the gap? __Mg + O₂ → 2MgO → 2Prompt: Count the Mg atoms on each side.
2H₂O₂ → 2H₂O + O₂ How many O atoms are on the right side of this balanced equation? → 4Prompt: Multiply the big number in front by the small number after the symbol.
Which equation is correctly balanced? (CH₄ + 2O₂ → CO₂ + 2H₂O / CH₄ + 2O₂ → CO₂ + 3H₂O / 2CH₄ + 2O₂ → CO₂ + 2H₂O / CH₄ + 2O₂ → 2CO₂ + 2H₂O) → CH₄ + 2O₂ → CO₂ + 2H₂OPrompt: Count each type of atom on both sides.

Hook · 3 min

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

I do: model it · 7 min

Work through the example out loud, saying why you do each step, not just what you do.
Example: How many moles are in 3.6 g of water (H₂O, Mr = 18)?
Step 1: 3.6 ÷ 18 = 0.2
Step 2: So the answer is: 0.2 mol
Answer: 0.2 mol
Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

Do these together. Students try each step on whiteboards before you reveal it.
Use the hints as prompts rather than giving the answer.

How many moles are in 88 g of carbon dioxide (CO₂, Mr = 44)? → 2 molPrompt: moles = mass ÷ Mr
What is the mass of 0.1 mol of magnesium oxide (MgO, Mr = 40), in g? → 4 gPrompt: mass = moles × Mr

You do: independent practice · 7 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 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

What is the mass of 0.5 mol of calcium carbonate (CaCO₃, Mr = 100), in g? → 50 gPrompt: mass = moles × Mr
CaCO₃ → CaO + CO₂. What mass of carbon dioxide is released when 200 g of calcium carbonate decomposes? (Mr: CaCO₃ = 100, CO₂ = 44) → 88 gPrompt: Find the moles of calcium carbonate.

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: Balancing chemical 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: Count particles with the Avogadro constant; Volumes of gases from moles (24 dm³ at RTP); Concentration in mol/dm³.
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-11.

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