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Science lesson plan · 8th grade (Year 9 in England) · 30 minutes

Diffusion, osmosis or active transport?

Cells, genetics and evolution

CCSS NGSS.HS-LS1-2England: GCSE Combined Science: Cell biology

Objective and success criteria

Students will: Diffusion, osmosis or active transport?.

  • 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: Osmosis and percentage change in mass

Leads to: Membrane structure, protein channels and bulk transport

Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Osmosis and percentage change in mass). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. A potato cylinder had a mass of 2.4 g. After 30 minutes in a sugar solution its mass was 2.76 g. What is the percentage change in mass? (Use a minus sign for a loss.) → 15 %Prompt: percentage change = (final − initial) ÷ initial × 100
  2. Potato pieces were left in sugar solutions. Percentage change in mass: 0 mol/dm³: +9 % 0.2 mol/dm³: +3 % 0.4 mol/dm³: −3 % 0.6 mol/dm³: −9 % 0.8 mol/dm³: −15 % Between which concentrations is the solution that matches the concentration inside the potato cells? (0–0.2 mol/dm³ / 0.2–0.4 mol/dm³ / 0.4–0.6 mol/dm³ / 0.6–0.8 mol/dm³) → 0.2–0.4 mol/dm³Prompt: Where there is no net movement of water, the mass does not change.
  3. Why does a plant cell in pure water not burst? (Its vacuole pumps water out / Chloroplasts absorb the water / Its strong cell wall stops it expanding too far, so it becomes turgid / It cannot take in water) → Its strong cell wall stops it expanding too far, so it becomes turgidPrompt: Which structure do plant cells have that animal cells lack?

Hook · 3 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: Diffusion, osmosis or active transport?. 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: Which process is this: urea passing from cells into the blood?
  • Step 1: Diffusion: particles move down a concentration gradient with no energy needed.
  • Step 2: So the answer is: diffusion
  • Answer: diffusion
  • 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. Which process is this: carbon dioxide entering a leaf? (diffusion / osmosis / active transport) → diffusionPrompt: Is it water specifically? Is it going against the gradient?
  2. Root hair cells contain many mitochondria. What does this suggest? (They absorb water only by diffusion / They use active transport, which needs energy / They do not respire / They photosynthesise) → They use active transport, which needs energyPrompt: What do mitochondria provide?

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. Transport in cells: which statement is true? (Osmosis needs energy from respiration. / Active transport can move substances from a low to a high concentration. / Water moves by osmosis from a concentrated to a dilute solution. / Active transport only happens in plants.) → Active transport can move substances from a low to a high concentration.Prompt: Which process needs energy?
  2. A poison stops respiration in root cells. Which process stops first? (diffusion of oxygen / active transport of mineral ions / all three equally / osmosis of water) → active transport of mineral ionsPrompt: Only one process needs energy from respiration.

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: Osmosis and percentage change in mass.
  • Use concrete materials: microscope images or slides.
  • 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: Membrane structure, protein channels and bulk transport.
  • 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-8.

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

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Diffusion, osmosis or active transport?

Name

Date

Score/ 6

  1. Question 1

    Which process is this: a raisin swelling in water?

    • A. diffusion
    • B. osmosis
    • C. active transport

  2. Question 2

    Glucose is absorbed from the small intestine even when the blood already holds more glucose than the gut. How?

    • A. by active transport, using energy from respiration
    • B. it cannot be absorbed
    • C. by diffusion down the gradient
    • D. by osmosis

  3. Question 3

    Transport in cells: which statement is true?

    • A. Osmosis needs energy from respiration.
    • B. Water moves by osmosis from a concentrated to a dilute solution.
    • C. Active transport only happens in plants.
    • D. Diffusion is faster when the gradient is steeper.

  4. Question 4

    Which process is this: urea passing from cells into the blood?

    • A. diffusion
    • B. osmosis
    • C. active transport

  5. Question 5

    A poison stops respiration in root cells. Which process stops first?

    • A. all three equally
    • B. diffusion of oxygen
    • C. active transport of mineral ions
    • D. osmosis of water

  6. Question 6

    Which process is this: mineral ions entering root hairs from soil with fewer ions?

    • A. diffusion
    • B. osmosis
    • C. active transport

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Answer key: Diffusion, osmosis or active transport?

  1. 1. B. osmosis

  2. 2. A. by active transport, using energy from respiration

  3. 3. D. Diffusion is faster when the gradient is steeper.

  4. 4. A. diffusion

  5. 5. C. active transport of mineral ions

  6. 6. C. active transport