Science lesson plan · 11th grade (Year 12 in England) · 45 minutes
Percentage yield
Chemical reactions, acids and bases
CCSS NGSS.HS-PS1-7England: GCSE Chemistry: Quantitative chemistry (yield)
Objective and success criteria
Students will: Percentage yield.
- 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: Moles and reacting masses
Leads to: Find the limiting reactant and how much product forms
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 (Moles and reacting masses). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- How many moles are in 50 g of calcium carbonate (CaCO₃, Mr = 100)? → 0.5 molPrompt: moles = mass ÷ Mr
- What is the mass of 4 mol of methane (CH₄, Mr = 16), in g? → 64 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.
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: Percentage yield. 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: A reaction could make 20 g of product in theory, but 9 g was actually collected. What is the percentage yield?
- Step 1: 9 ÷ 20 × 100 = 45
- Step 2: So the answer is: 45 %
- Answer: 45 %
- 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.
- A reaction could make 120 g of product in theory, but 72 g was actually collected. What is the percentage yield? → 60 %Prompt: percentage yield = actual mass ÷ theoretical mass × 100
- CaCO₃ → CaO + CO₂ (Mr: CaCO₃ = 100, CaO = 56). 25 g of calcium carbonate was heated and 11.2 g of calcium oxide was collected. What is the percentage yield? Give 1 decimal place. → 80 %Prompt: First work out the theoretical mass of CaO.
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.
- CaCO₃ → CaO + CO₂ (Mr: CaCO₃ = 100, CaO = 56). 20 g of calcium carbonate was heated and 10.08 g of calcium oxide was collected. What is the percentage yield? Give 1 decimal place. → 90 %Prompt: First work out the theoretical mass of CaO.
- A reaction could make 25 g of product in theory, but 15 g was actually collected. What is the percentage yield? → 60 %Prompt: percentage yield = actual mass ÷ theoretical mass × 100
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: Moles and reacting masses.
- 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: Find the limiting reactant and how much product forms.
- 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