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Science lesson plan · 11th grade (Year 12 in England) · 30 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 · 4 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.
  1. How many moles are in 1.8 g of water (H₂O, Mr = 18)? → 0.1 molPrompt: moles = mass ÷ Mr
  2. What is the mass of 0.1 mol of magnesium oxide (MgO, Mr = 40), in g? → 4 gPrompt: mass = moles × Mr
  3. 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 · 3 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 · 7 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 · 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.
  1. How many carbon atoms are in 3 mol? The Avogadro constant is 6.02 × 10²³ per mol. Give your answer as a number × 10²³ (to 2 decimal places). → 18.06Prompt: number of particles = moles × Avogadro constant
  2. A sample contains 1.806 × 10²⁴ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol) → 3 molPrompt: moles = number of particles ÷ Avogadro constant

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.
  1. A sample contains 3.01 × 10²³ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol) → 0.5 molPrompt: moles = number of particles ÷ Avogadro constant
  2. How many carbon atoms are in 3 mol? The Avogadro constant is 6.02 × 10²³ per mol. Give your answer as a number × 10²³ (to 2 decimal places). → 18.06Prompt: number of particles = moles × 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

eurekami

Count particles with the Avogadro constant

Name

Date

Score/ 6

  1. Question 1

    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).

    Answer

  2. Question 2

    How many atoms in total are in 0.5 mol of CH₄? (Avogadro constant = 6.02 × 10²³ per mol) Give your answer as a number × 10²³ (to 2 decimal places).

    Answer

  3. Question 3

    A sample contains 3.01 × 10²⁴ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol)

    Answermol

  4. Question 4

    How many carbon atoms are in 4 mol? The Avogadro constant is 6.02 × 10²³ per mol. Give your answer as a number × 10²³ (to 2 decimal places).

    Answer

  5. Question 5

    How many atoms in total are in 1 mol of CH₄? (Avogadro constant = 6.02 × 10²³ per mol) Give your answer as a number × 10²³ (to 2 decimal places).

    Answer

  6. Question 6

    A sample contains 1.806 × 10²⁴ molecules. How many moles is this? (Avogadro constant = 6.02 × 10²³ per mol)

    Answermol

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Answer key: Count particles with the Avogadro constant

  1. 1. 1.51

  2. 2. 15.05

  3. 3. 5 mol

  4. 4. 24.08

  5. 5. 30.1

  6. 6. 3 mol