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Science lesson plan · 8th grade (Year 9 in England) · 60 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 · 6 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 2.5 g. After 30 minutes in a sugar solution its mass was 2.25 g. What is the percentage change in mass? (Use a minus sign for a loss.) → -10 %Prompt: percentage change = (final − initial) ÷ initial × 100
  2. Potato pieces were left in sugar solutions. Percentage change in mass: 0 mol/dm³: +20 % 0.2 mol/dm³: +12 % 0.4 mol/dm³: +4 % 0.6 mol/dm³: −4 % 0.8 mol/dm³: −12 % 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) → 0.4–0.6 mol/dm³Prompt: Where there is no net movement of water, the mass does not change.
  3. A red blood cell is placed in pure water. What happens? (It swells and may burst because water enters by osmosis / It shrinks / Nothing changes / It grows a cell wall) → It swells and may burst because water enters by osmosisPrompt: Animal cells have no cell wall to resist swelling.

Hook · 6 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 · 12 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 · 12 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: oxygen entering the blood in the lungs? (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 photosynthesise / They absorb water only by diffusion / They use active transport, which needs energy / They do not respire) → They use active transport, which needs energyPrompt: What do mitochondria provide?

You do: independent practice · 17 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 · 7 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Which process is this: a raisin swelling in water? (diffusion / osmosis / active transport) → osmosisPrompt: Is it water specifically? Is it going against the gradient?
  2. Transport in cells: which statement is true? (Active transport only happens in plants. / Water moves by osmosis from a concentrated to a dilute solution. / Osmosis needs energy from respiration. / Active transport can move substances from a low to a high concentration.) → Active transport can move substances from a low to a high concentration.Prompt: Which process needs energy?

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/ 8

  1. Question 1

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

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

  2. Question 2

    Transport in cells: which statement is true?

    • A. Osmosis needs energy from respiration.
    • B. Active transport can move substances from a low to a high concentration.
    • C. Water moves by osmosis from a concentrated to a dilute solution.
    • D. Active transport only happens in plants.

  3. Question 3

    Which process is this: water entering root hair cells from moist soil?

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

  4. Question 4

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

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

  5. Question 5

    What do diffusion and osmosis have in common?

    • A. Both are passive: they need no energy from respiration
    • B. Both move substances against a gradient
    • C. Both move only water
    • D. Both need mitochondria

  6. Question 6

    Which process is this: oxygen entering the blood in the lungs?

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

  7. Question 7

    Root hair cells contain many mitochondria. What does this suggest?

    • A. They photosynthesise
    • B. They absorb water only by diffusion
    • C. They do not respire
    • D. They use active transport, which needs energy

  8. Question 8

    Which process is this: a raisin swelling in water?

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

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Answer key: Diffusion, osmosis or active transport?

  1. 1. C. by active transport, using energy from respiration

  2. 2. B. Active transport can move substances from a low to a high concentration.

  3. 3. B. osmosis

  4. 4. A. diffusion

  5. 5. A. Both are passive: they need no energy from respiration

  6. 6. A. diffusion

  7. 7. D. They use active transport, which needs energy

  8. 8. B. osmosis