Science lesson plan · 11th grade (Year 12 in England) · 45 minutes
Count particles with the Avogadro constant
Chemical reactions, acids and bases
CCSS NGSS.HS-PS1-7England: GCSE Combined Science: Quantitative chemistry (Higher)
Objective and success criteria
Students will: Count particles with the Avogadro constant.
- 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: the next skill in this area.
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 11.7 g of sodium chloride (NaCl, Mr = 58.5)? → 0.2 molPrompt: moles = mass ÷ Mr
- What is the mass of 1.5 mol of magnesium oxide (MgO, Mr = 40), in g? → 60 gPrompt: mass = moles × Mr
- 2Mg + O₂ → 2MgO. What mass of magnesium oxide forms from 12 g of magnesium? (Ar: Mg = 24, O = 16) → 20 gPrompt: Find the moles of magnesium first.
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: Count particles with the Avogadro constant. 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: How many oxygen molecules are in 0.5 mol? The Avogadro constant is 6.02 × 10²³ per mol. Give your answer as a number × 10²³ (to 2 decimal places).
- Step 1: 0.5 × 6.02 = 3.01
- Step 2: So 3.01 × 10²³
- Step 3: So the answer is: 3.01
- Answer: 3.01
- 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.
- How many water molecules are in 0.25 mol? The Avogadro constant is 6.02 × 10²³ per mol. Give your answer as a number × 10²³ (to 2 decimal places). → 1.51Prompt: number of particles = moles × Avogadro constant
- A sample contains 3.01 × 10²⁴ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol) → 5 molPrompt: moles = number of particles ÷ Avogadro constant
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.
- How many atoms in total are in 2 mol of NH₃? (Avogadro constant = 6.02 × 10²³ per mol) Give your answer as a number × 10²³ (to 2 decimal places). → 48.16Prompt: First count the atoms in one molecule.
- A sample contains 1.204 × 10²⁴ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol) → 2 molPrompt: moles = number of particles ÷ Avogadro constant
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
- 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