Diffusion · Year 7

Year 7 · Chemistry and particle ideas · original lesson pack

DASKEREL beta · internal AI review pending

Diffusion: moving particles

Official curriculum or provision guidance

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Explain diffusion using random particle motion
Distinguish movement in both directions from net movement
Predict how a concentration difference changes over time in a closed system

Vocabulary: particle · concentration · random motion · concentration gradient · net movement

Retrieve previous learning

How does the particle model describe a gas or a liquid?

Check: Its particles are in constant motion and can move past one another; they are not fixed in a rigid pattern as in a solid.

Learn the concept

A substance in a liquid or gas consists of particles too small to see individually. They move in many directions and collide. Concentration means how much of that substance occupies a given volume. When two regions of equal volume contain different numbers of its particles, the more crowded region has the higher concentration. Compare equal volumes before deciding which side is higher; simply counting particles in unequal-sized containers is misleading.

Diffusion is the net movement of particles of a substance from higher to lower concentration because of their random motion. Individual particles cross both ways. While there are more particles per unit volume on one side, more usually cross away from that side than return in the same interval. This overall difference is net movement; no particle knows which direction to travel and no energy-driven pump is required for ordinary diffusion.

Imagine a drop of soluble dye entering still water. After the dye mixes into the water, its particles spread away from the initially concentrated region. The visible colour becomes more even, but the particles keep moving after the colour looks uniform. In a closed container with no reaction, the amount of dye is conserved. Diffusion does not mean that water particles turn into dye or that all dye particles move along a single arrow. The same particle reasoning can describe a gas spreading from a region of higher concentration into still air. A scent noticed across a room is not proof of diffusion alone, however, because bulk airflow may also carry it.

A larger concentration difference often gives a greater net movement under otherwise comparable conditions. Temperature can also affect particle motion, but a fair comparison changes only the factor being investigated and records time, volumes and starting amounts. This written model cannot show individual particles; observations and measurements support the explanation rather than directly displaying their paths.

Worked model

Fictional equal-volume regions A and B contain 60 and 20 dye particles. A has the higher concentration because the volumes are equal.
During one illustrative time interval, 12 dye particles cross A to B and 4 cross B to A. Net movement is 12 - 4 = 8 particles from A to B, although particles moved both ways.
If the regions remain connected and no dye is lost, repeated intervals tend to reduce the concentration difference. At equal concentration, random crossings continue but their average rates balance.
For a gas, use the same net-flow reasoning across a still-air model. Qualify a real room observation because airflow can transport the gas as well.

Guided practice

In one interval, 15 particles cross left to right and 9 cross right to left. Which way is net movement and how large is it?

Hint: Subtract the opposing crossings; do not erase the smaller flow.

Check the guided answer

Net movement is 6 particles left to right. Nine still crossed the other way.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“All particles travel from high concentration to low concentration and stop once spread out.”

Correction: Particles move randomly in both directions throughout. Diffusion describes the net effect while a concentration difference exists; equal concentration does not stop individual motion.

Extend and reflect

Design a fair classroom observation to compare dye spreading at two temperatures without doing it unsupervised.

Guidance: A teacher approves the materials and method; use the same dye amount, water volume, vessel and observation times. State that temperature may also change mixing, so do not treat one observation as direct proof of a particle path.

Take the end-of-unit check

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Chemistry and Materials Science

This lesson practises: Explain diffusion using random particle motion. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Chemistry and Materials Science. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 7 · Working scientifically · original lesson pack

DASKEREL beta · internal AI review pending

Diffusion through a permeable material: practical reasoning

Open this lesson's library record

Official curriculum or provision guidance

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Explain how a permeable material allows suitable particles through
Interpret a fictional cube penetration dataset
Plan a fair, supervised comparison and state its limits

Vocabulary: permeable · penetration depth · variable · fair test · prediction

Retrieve previous learning

What makes net movement different from the motion of one particle?

Check: A particle moves randomly; net movement compares opposing flows of many particles over an interval.

Learn the concept

A material is permeable to a substance if that substance can pass through it. Jelly looks solid to the eye but can contain a water-filled network through which some dissolved particles move. The extent of a colour change inside a prepared cube can provide indirect evidence of penetration. The visible boundary is a marker for an interaction in the model, not a photograph of individual particles.

For safety, DASKEREL supplies fictional measurements rather than instructions for preparing chemical indicator cubes. Any classroom demonstration using indicators, acids or other reagents requires a teacher's risk assessment, suitable equipment, supervision and disposal. Do not reproduce a demonstration at home from this lesson. A written answer can interpret results but cannot establish safe or competent practical technique.

Consider two fictional cubes observed for the same time. Cube A has a 10 mm side and a 2 mm changed layer measured inward from each face; its unchanged central side is 10 - 2 - 2 = 6 mm. Cube B has a 20 mm side and the same 2 mm layer; its central side is 16 mm. The smaller cube has a larger proportion of its side affected, but these data alone do not show that particles moved faster inside A.

To test temperature, keep cube composition and size, surrounding liquid concentration and volume, time, measurement rule and stirring the same, changing only temperature under teacher control. To test cube size, keep temperature and other factors the same. Repeat measurements, record uncertainty at a fuzzy colour boundary and compare patterns without claiming that one result proves a universal law. In invented equal-size cube data, a cool group has a 1 mm changed layer and a warmer group a 3 mm layer after the same time. This is consistent with faster penetration in the warmer condition, but only if the other conditions were controlled; it does not directly show individual particle speed.

Worked model

Record the invented observation at the same time point: A side 10 mm, B side 20 mm, each showing 2 mm penetration from every face.
Calculate unchanged core side lengths: A 10 - 4 = 6 mm; B 20 - 4 = 16 mm. State that the calculation assumes a uniform 2 mm layer from opposite faces.
Compare the unchanged fraction of each side: 6/10 = 0.60 for A, 16/20 = 0.80 for B. The smaller cube has a smaller unchanged fraction; the penetration distance was the same.
Conclude only that these fictional measurements fit diffusion through a permeable material. Actual rates, cube consistency and practical technique would need supervised observations and repeats. For the separate fictional temperature comparison, equal-sized cubes show 1 mm changed at a cooler condition and 3 mm at a warmer condition after equal times. Predict a deeper changed layer when particles have more kinetic energy, then check whether temperature was the only planned variable.

Guided practice

A 12 mm fictional cube has a 3 mm changed layer from each opposite face. What is the unchanged central side length?

Hint: Subtract the layer on both sides.

Check the guided answer

12 - 3 - 3 = 6 mm, assuming even penetration and opposite faces.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“A jelly cube is solid, so no particles can pass through it.”

Correction: A permeable material can allow some particles through even if it holds its overall shape. The observation depends on the material and substance used.

Extend and reflect

Compare the proportion of side length changed in the two fictional cubes, and propose a repeatable recording method.

Guidance: For A, 4/10 = 40%; for B, 4/20 = 20% when both faces are counted. Define the measurement time and boundary rule, and have a teacher approve any real practical work.

Take the end-of-unit check

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Physical Sciences

This lesson practises: Explain how a permeable material allows suitable particles through. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Physical Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Data Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 7 · Biology · original lesson pack

DASKEREL beta · internal AI review pending

Diffusion through the cell membrane

Open this lesson's library record

Official curriculum or provision guidance

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Explain net diffusion of a named substance across a cell membrane
Distinguish a selective living membrane from a simple permeable model
Explain why equilibrium does not mean particles stop moving

Vocabulary: cell membrane · selectively permeable · oxygen · carbon dioxide · passive movement

Retrieve previous learning

What does net movement mean when particles cross a boundary in both directions?

Check: It is the difference between opposing flows. When more of a substance crosses one way than the other, that substance has a net direction.

Learn the concept

Every cell has a cell membrane separating its inside from its surroundings. Some substances can cross it, but the membrane is selective: whether a substance passes depends on its properties and available pathways. A classroom drawing of a boundary with holes is a model, not a literal picture of all membranes. A membrane does not make a conscious choice about which particle it wants.

Oxygen can move into a respiring cell when its concentration is higher outside than inside and a suitable route through the membrane is available. Carbon dioxide can move out when its concentration is higher inside. Consider each substance separately: the oxygen gradient need not point the same way as the carbon dioxide gradient. Diffusion is passive net movement, rather than a cell pulling a substance in with intention.

At a given moment, oxygen particles may cross both into and out of the cell. A higher concentration outside means that, on average, more can cross inward than outward over a comparable interval. If the concentrations become equal and nothing consumes or produces oxygen, crossings still occur but average opposing flows balance. In a living cell, respiration may use oxygen and help maintain a concentration difference.

A diagram may show a broad arrow for net movement, but it must not erase the opposite individual crossings. A real cell has many interacting processes, and not all membrane transport is diffusion. To justify a diffusion claim, name the substance, compare its concentrations on the two sides, check that it can cross by an appropriate pathway, and state the net direction under the stated conditions.

Worked model

In a fictional model, oxygen concentration is 12 arbitrary units outside a cell and 5 inside. The proposed net direction for oxygen is inward, provided oxygen can cross the membrane.
Over an illustrative interval, 9 oxygen particles cross inward and 3 outward. Net oxygen movement is 9 - 3 = 6 inward; both individual directions occurred.
In the same model, carbon dioxide is 8 units inside and 2 outside. Its net direction is outward. This does not contradict inward oxygen diffusion because each substance has its own gradient.
If both sides of one substance later reach equal concentration in a closed model, report no average net movement, not that the particles freeze.

Guided practice

A cell model shows carbon dioxide at 7 units inside and 3 outside. Predict its net direction and name one assumption.

Hint: Compare carbon dioxide with carbon dioxide, and consider membrane passage.

Check the guided answer

Net carbon dioxide movement is outward if the membrane permits it to cross by a suitable pathway.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“The cell deliberately draws oxygen through tiny holes in its membrane.”

Correction: Diffusion is passive random particle movement with a net direction set by the substance's concentration gradient and its ability to cross. The membrane is not a conscious filter or a universally perforated sheet.

Extend and reflect

Why might an oxygen gradient persist around a respiring cell even while oxygen crosses inward?

Guidance: Explain that oxygen is used in respiration and may also be replenished outside. Distinguish this open living situation from a closed, non-reacting classroom model.

Take the end-of-unit check

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Biological and Computational Sciences

This lesson practises: Explain net diffusion of a named substance across a cell membrane. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Biological and Computational Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Bioinformatics Technician. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 7 · Biology · original lesson pack

DASKEREL beta · internal AI review pending

Diffusion through a selectively permeable membrane: practical reasoning

Open this lesson's library record

Official curriculum or provision guidance

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Interpret evidence for movement through a model membrane
Calculate a net transfer without claiming one-way particle motion
Evaluate the model and plan a fair supervised comparison

Vocabulary: selectively permeable · membrane model · observation · inference · control variable

Retrieve previous learning

Does equal concentration imply that particles have stopped moving?

Check: No. Average opposing crossings can balance while individual particles still move.

Learn the concept

A selectively permeable model membrane lets some substances pass under the conditions of the model while others do not readily pass. In a school demonstration, a teacher may use a tubing membrane and indicator observations. The visible result is evidence to interpret, not a view of individual particles. Real cell membranes are biologically more complex than this model and do not behave exactly like a sheet of uniform holes.

DASKEREL uses fictional chamber data instead of preparation instructions. A live demonstration involving reagents, staining solutions or tubing is for a teacher with an approved risk assessment, equipment, supervision and disposal plan. Do not attempt to reproduce it at home. A written check can assess reasoning from observations; it cannot certify practical handling or safe technique.

Imagine equal-volume chambers A and B separated by a model membrane that lets substance X cross. At first A contains 40 counted X particles and B contains 10. Later A contains 27 and B contains 23, with no loss or reaction. Both totals are 50. The observed net transfer is 13 particles from A to B. The before-and-after totals do not reveal how many particles crossed in each direction during the interval.

To test selective passage, compare the behaviour of named substances and record an observation for each. Keep chamber volume, initial concentration, time and temperature defined, and use a control or repeat where possible. A colour change may be indirect evidence of movement or reaction; the explanation must separate what was seen from what is inferred. A membrane model cannot alone establish every route across a living cell membrane. In a second fictional observation, substance Y remains at 10 counted units on each side while X changes; with a suitable Y-specific detection method and control this supports selective passage under these conditions. Without such a method, an absent colour change alone cannot prove that Y did not cross.

Worked model

Label the fictional observations: equal-volume A has 40 X particles before and 27 after; equal-volume B has 10 before and 23 after.
Check conservation in the stated closed model: 40 + 10 = 50 before and 27 + 23 = 50 after.
Calculate the net change: A loses 13 and B gains 13, so net X transfer is 13 from A to B. Do not claim that exactly 13 particles crossed or that none crossed back.
State an evidence limit: end counts show net transfer through the model under the stated closed, non-reacting and no-loss assumptions, but not individual paths, membrane structure or the behaviour of every other substance. The separate Y observation requires a Y-specific control before claiming selective passage.

Guided practice

If A falls from 30 to 24 and B rises from 10 to 16 in equal-volume chambers, what is the net transfer?

Hint: Compare each chamber's before and after counts, then check the total.

Check the guided answer

The net transfer is 6 particles from A to B; totals are 40 both before and after.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“A colour change proves that only one type of particle moved one way and that a real cell works identically.”

Correction: Colour is indirect evidence under stated conditions. Particles may move both ways, other substances need their own evidence, and tubing is a limited model of a living membrane.

Extend and reflect

A model shows no visible colour change for substance Y. Give two distinct explanations and a better evidence plan.

Guidance: Y might not cross the membrane under these conditions, or the indicator might be insensitive to Y or the observation time too short. A teacher-selected control and suitable detection method can distinguish these possibilities.

Take the end-of-unit check

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Biological and Computational Sciences

This lesson practises: Interpret evidence for movement through a model membrane. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Biological and Computational Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Bioinformatics Technician. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.