Science lesson plan · 7th grade (Year 8 in England) · 60 minutes
Diffusion: how particles spread out
Cells, genetics and evolution
CCSS NGSS.MS-LS1-2CCSS NGSS.MS-PS1-4England: KS3 Biology: Cells and organisationEngland: GCSE Combined Science: Cell biology
Objective and success criteria
Students will: Diffusion: how particles spread out.
- 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: The particle model; Plant and animal cells
Leads to: Osmosis and percentage change in mass; Surface area to volume ratio and exchange
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 (The particle model; Plant and animal cells). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Which state is described: particles with lots of empty space between them? (solid / liquid / gas) → gasPrompt: How close are the particles, and how do they move?
- Why does the smell of perfume spread across a room? (Perfume particles are attracted to noses / The perfume pushes the air away / Perfume particles diffuse, moving randomly among the air particles / Air particles stand still) → Perfume particles diffuse, moving randomly among the air particlesPrompt: Particles in gases move in all directions.
- Which state is described: particles packed in a regular pattern? (solid / liquid / gas) → solidPrompt: How close are the particles, and how do they move?
Hook · 6 min
- Show a microscope image of cells and ask what students think they are looking at.
- Share the objective: Diffusion: how particles spread out. 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: Carbon dioxide made by respiring cells moves into the blood. Which way is the gradient?
- Step 1: Cells make carbon dioxide, so it diffuses from cells into the blood.
- Step 2: So the answer is: higher in the cells, lower in the blood
- Answer: higher in the cells, lower in the blood
- 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.
- Which change would make diffusion faster? (a higher temperature / a thicker membrane / a lower temperature / a smaller surface area) → a higher temperaturePrompt: Think about how fast the particles move.
- Purple dye spread 15 mm through a block of jelly in 3 hours. What was the mean rate of diffusion, in mm per hour? → 5 mm/hPrompt: rate = distance ÷ time
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.
- Diffusion: which statement is NOT true? (Diffusion happens in gases and liquids. / Diffusion stops completely when the room is cold. / A larger surface area speeds up diffusion. / A steeper concentration gradient gives faster diffusion.) → Diffusion stops completely when the room is cold.Prompt: Which direction is the net movement?
- Carbon dioxide made by respiring cells moves into the blood. Which way is the gradient? (higher in the cells, lower in the blood / there is no carbon dioxide in cells / higher in the blood, lower in the cells / the same on both sides) → higher in the cells, lower in the bloodPrompt: Where is carbon dioxide being made?
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: The particle model.
- 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: Osmosis and percentage change in mass; Surface area to volume ratio and exchange.
- 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-7.
Free lesson plan from eurekami.com/lesson-plan-builder