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Science lesson plan · 11th grade (Year 12 in England) · 45 minutes

Concentration in mol/dm³

Chemical reactions, acids and bases

CCSS NGSS.HS-PS1-7England: GCSE Chemistry: Quantitative chemistry (concentration of solutions, Higher)

Objective and success criteria

Students will: Concentration in mol/dm³.

  • 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: Concentration in grams per dm³; Moles and reacting masses

Leads to: Titration calculations; Dilution calculations (c₁V₁ = c₂V₂)

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 (Concentration in grams per dm³; Moles and reacting masses). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. 20 g of sodium hydroxide is dissolved to make 0.5 dm³ of solution. What is the concentration, in g/dm³? → 40 g/dm³Prompt: concentration = mass of solute ÷ volume of solution
  2. How many moles are in 20 g of sodium hydroxide (NaOH, Mr = 40)? → 0.5 molPrompt: moles = mass ÷ Mr
  3. 1.6 g of copper sulfate is dissolved in water to make 100 cm³ of solution. What is the concentration, in g/dm³? (1 dm³ = 1000 cm³) → 16 g/dm³Prompt: Convert cm³ to dm³ by dividing by 1000.

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: Concentration in mol/dm³. 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: 0.05 mol of hydrochloric acid is in 250 cm³ of solution. What is the concentration, in mol/dm³?
  • Step 1: 250 ÷ 1000 = 0.25 dm³
  • Step 2: 0.05 ÷ 0.25 = 0.2
  • Step 3: So the answer is: 0.2 mol/dm³
  • Answer: 0.2 mol/dm³
  • 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.
  1. 0.0625 mol of hydrochloric acid is in 250 cm³ of solution. What is the concentration, in mol/dm³? → 0.25 mol/dm³Prompt: concentration = moles ÷ volume in dm³
  2. How many moles of sodium hydroxide are in 20 cm³ of a 0.5 mol/dm³ solution? → 0.01 molPrompt: moles = concentration × volume in dm³

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.
  1. What mass of sodium chloride (NaCl, Mr = 58.5) is needed to make 100 cm³ of 0.2 mol/dm³ solution, in g? Give 2 decimal places. → 1.17 gPrompt: Find the moles needed first.
  2. 0.4 mol of hydrochloric acid is in 200 cm³ of solution. What is the concentration, in mol/dm³? → 2 mol/dm³Prompt: concentration = moles ÷ volume in dm³

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: Concentration in grams per dm³.
  • 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: Titration calculations; Dilution calculations (c₁V₁ = c₂V₂).
  • 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

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Concentration in mol/dm³

Name

Date

Score/ 8

  1. Question 1

    1 mol of hydrochloric acid is in 500 cm³ of solution. What is the concentration, in mol/dm³?

    Answermol/dm³

  2. Question 2

    What mass of sodium hydroxide (NaOH, Mr = 40) is needed to make 500 cm³ of 0.2 mol/dm³ solution, in g? Give 2 decimal places.

    Answerg

  3. Question 3

    How many moles of sodium hydroxide are in 50 cm³ of a 1.5 mol/dm³ solution?

    Answermol

  4. Question 4

    0.25 mol of hydrochloric acid is in 500 cm³ of solution. What is the concentration, in mol/dm³?

    Answermol/dm³

  5. Question 5

    What mass of sodium hydroxide (NaOH, Mr = 40) is needed to make 500 cm³ of 0.1 mol/dm³ solution, in g? Give 2 decimal places.

    Answerg

  6. Question 6

    0.05 mol of hydrochloric acid is in 200 cm³ of solution. What is the concentration, in mol/dm³?

    Answermol/dm³

  7. Question 7

    What mass of sodium hydroxide (NaOH, Mr = 40) is needed to make 100 cm³ of 0.2 mol/dm³ solution, in g? Give 2 decimal places.

    Answerg

  8. Question 8

    0.02 mol of hydrochloric acid is in 100 cm³ of solution. What is the concentration, in mol/dm³?

    Answermol/dm³

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Answer key: Concentration in mol/dm³

  1. 1. 2 mol/dm³

  2. 2. 4 g

  3. 3. 0.075 mol

  4. 4. 0.5 mol/dm³

  5. 5. 2 g

  6. 6. 0.25 mol/dm³

  7. 7. 0.8 g

  8. 8. 0.2 mol/dm³