Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. It results from constant random particle motion and continues until particles are more evenly distributed. Higher temperature usually increases diffusion rate because particles move faster.
Example
Food colouring spreads through still water without stirring because its particles and water particles are constantly moving and colliding.
Key terms
Diffusion:
Net movement from higher to lower concentration.
Concentration:
Amount of a substance in a given volume.
Random motion:
Unpredictable movement of particles in many directions.
Questions
1. Which statement best captures diffusion and particle motion?
Diffusion results from random particle motion and produces a more even distribution over time.
Diffusing particles move in one planned direction because they know where empty space is.
The pattern can only be explained by guessing.
The topic has no observable evidence.
2. Which term means "Net movement from higher to lower concentration."?
Diffusion
Concentration
Random motion
Variable
3. Which term means "Amount of a substance in a given volume."?
Concentration
Diffusion
Random motion
Conclusion
4. Which term means "Unpredictable movement of particles in many directions."?
Random motion
Diffusion
Concentration
Prediction
5. Which observation task is most relevant to this topic?
Watch a drop of food colouring spread through still water and record changes at regular time intervals.
Copy the topic title without looking at an example.
Choose a result before making observations.
Ignore details that do not match a first guess.
6. Which model would best represent the key process or relationship?
Use a before-and-after particle diagram to show net movement from high to low concentration.
A decorative drawing with no labels or connection to evidence.
A list of unrelated facts.
A model that deliberately contradicts every observation.
7. Which investigation is focused most directly on the scientific idea?
Compare diffusion in cool and warm water while keeping container size and drop size the same.
Change many uncontrolled factors and record nothing.
Ask only for opinions and treat them as measurements.
Repeat a memorised answer without testing it.
8. Which evidence best supports the lesson explanation?
Colour usually spreads faster in warmer water, supporting the model that warmer particles move more rapidly.
Diffusing particles move in one planned direction because they know where empty space is.
One preferred answer with no observation.
A claim that cannot be checked in any way.
9. Which task applies the science in a new context?
Explain how oxygen can diffuse from alveoli into blood across a very thin membrane.
Write the heading again without explaining it.
Ignore the system and choose randomly.
Assume the same answer fits every situation.
10. Which response best corrects the misconception in this topic?
Diffusion results from random particle motion and produces a more even distribution over time.
Diffusing particles move in one planned direction because they know where empty space is.
Both statements must be equally correct.
Evidence cannot help decide between explanations.
11. What makes a scientific observation useful?
It records relevant details without changing them to fit an expectation.
It includes only details that support a preferred answer.
It replaces measurements with guesses.
It hides the conditions under which it was made.
12. Why should a scientific model include its limitations?
Models simplify reality, so users need to know what the representation leaves out.
A limitation proves the model has no value.
Models are exact copies and never omit anything.
Limitations should be hidden so a model looks certain.
13. What makes a comparative investigation fair?
Change or compare the intended factor while keeping other relevant conditions consistent.
Change every condition at the same time.
Measure only the result that looks best.
Decide the conclusion before collecting data.
14. Why repeat measurements or use several samples?
To reveal variation and reduce the influence of chance or one unusual result.
To guarantee a preferred conclusion.
To make units unnecessary.
To remove the need for a clear method.
15. What is the best response to an anomalous result?
Record it, check the method and investigate whether it is error or meaningful variation.
Delete it automatically.
Delete all other results instead.
Assume it proves the whole topic wrong.
16. Which conclusion is scientifically responsible?
One that answers the question, uses the evidence and states important limits.
One that claims more than the data show.
One that ignores conflicting evidence.
One based only on the expected answer.
17. What would make the claim about diffusion and particle motion stronger?
Several relevant, repeatable evidence lines that agree with the explanation.
A larger heading and no new evidence.
Removing results that are inconvenient.
Relying on a single uncheckable opinion.
18. What should happen if reliable new evidence conflicts with a model?
The model should be reviewed and revised or replaced if needed.
The evidence should always be hidden.
The original model must never change.
Scientists should stop asking questions.
19. How should safety and ethics shape an investigation?
Risks, people, living things and environments should be considered before the method is used.
Safety matters only after data collection.
Any method is acceptable if it is fast.
Ethics has no place in science.
20. What makes science communication trustworthy?
Clear methods, accurate terms, relevant evidence and acknowledgement of uncertainty.
Certainty without evidence.
Leaving out how results were obtained.
Using dramatic language instead of data.
21. What is the strongest overall outcome from studying diffusion and particle motion?
Use observations, models, investigations and evidence to explain and apply this idea.
Memorise the title without using it.
Avoid testing explanations.
Treat every first idea as permanently correct.
Answer key (parent copy)
1. Diffusion results from random particle motion and produces a more even distribution over time.
2. Diffusion
3. Concentration
4. Random motion
5. Watch a drop of food colouring spread through still water and record changes at regular time intervals.
6. Use a before-and-after particle diagram to show net movement from high to low concentration.
7. Compare diffusion in cool and warm water while keeping container size and drop size the same.
8. Colour usually spreads faster in warmer water, supporting the model that warmer particles move more rapidly.
9. Explain how oxygen can diffuse from alveoli into blood across a very thin membrane.
10. Diffusion results from random particle motion and produces a more even distribution over time.
11. It records relevant details without changing them to fit an expectation.
12. Models simplify reality, so users need to know what the representation leaves out.
13. Change or compare the intended factor while keeping other relevant conditions consistent.
14. To reveal variation and reduce the influence of chance or one unusual result.
15. Record it, check the method and investigate whether it is error or meaningful variation.
16. One that answers the question, uses the evidence and states important limits.
17. Several relevant, repeatable evidence lines that agree with the explanation.
18. The model should be reviewed and revised or replaced if needed.
19. Risks, people, living things and environments should be considered before the method is used.
20. Clear methods, accurate terms, relevant evidence and acknowledgement of uncertainty.
21. Use observations, models, investigations and evidence to explain and apply this idea.