A model is a tool, not a photograph. The particle model explains conduction, convection and static charge; the wave model explains sound, reflection, refraction and the electromagnetic spectrum. Light shows both wave-like and particle-like behaviour, so neither model alone explains it all: each is useful for some phenomena and weak for others.
Is light a wave or a stream of particles? Scientists argued for 300 years. The answer turned out to be: the question is a bit too simple.
A short lesson with no simulation. You have used two models this unit. Now you decide where each one works.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explain: Use the particle model to explain what you saw.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: who is right?
ExplainUse the particle model to explain what you saw.
Explain: where each model works
In your book: choose two phenomena from this unit, one explained best by the wave model and one by the particle model. For each, name the model and write one sentence saying why it fits.
Which model explains it best?
An echo: sound bouncing back off a cliffSound reflects, like any wave.
Heat passing along a metal spoonCollisions between particles pass the energy on.
Light bending as it goes into glassThe wave fronts slow down and turn.
Warm water rising in a potBulk movement of particles, driven by density.
A higher note having a shorter wavelength
A balloon charged by rubbingElectrons move from one material to the other.
Elaborate TypicalUse the same idea in a new context.
Elaborate: evaluate
Elaborate WiderUse the same idea in a new context.
Elaborate: photons
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Write one sentence: "At first I thought… Now I think… because…"
Revision summary
The particle model explains conduction, convection and static charge; the wave model explains sound, reflection, refraction and the electromagnetic spectrum.
Light behaves like a wave when it bends and spreads, and like photons when it gives energy to single electrons.
A scientific model is a tool with a domain of usefulness, not a literal picture of reality.
For teachers
Students evaluate the wave and particle models against phenomena from the unit, say where each succeeds and fails, and explain that models are tools with domains of usefulness (AC9S9U04, node 5, an integration node). About 15 minutes.
I can say which model explains each phenomenon best.
I can say where a model stops working.
I can explain why models are tools, not copies of reality.
Before class
A short questions-led lesson with no simulation, an integration node that pulls the unit together. Set the width with ?width=minimum, typical (default) or wider. It follows How does light bend?
The photon material is a first look, not a full treatment: the aim is for students to see that a good model can still have limits, and that scientists combine models. Don't introduce wave-particle duality as mysterious; say that light is modelled in two ways and the choice depends on the question.
Board notes: none; the lesson has no board. The in-your-book task is the main output, and a class discussion of the sorted list works better than the screen.
Running the lesson
Engage: tally the predictions. Ask the 'one is right' group what experiment could settle it.
Explain: the sort and the 'models are tools' question are the success criteria.
In your own words: two phenomena, two models, two sentences.
The hard part (on purpose)
Moving from 'which model is true' to 'which model is useful for this question'. When a student asks which model is correct, ask what the model needs to do in this case.
When students get stuck
A student says the particle model is wrong because it doesn't explain sound. Ask: What does it explain well? Fix: Conduction and convection. A model is judged by what it is used for.
A student says light is both a wave and a particle at once. Ask: In which experiments does it act like each? Fix: Like a wave when it bends and spreads, like photons when it hands over energy to single electrons. It is one thing described by two models.
Stretch and support
Stretch: Can you think of a model from another subject that is a useful tool but not a literal copy? (A map, a circuit diagram, the water-flow model of electricity.)
Support: Give a two-column table (Wave model, Particle model) with the six phenomena on slips to place, and a sentence starter for each: 'The ___ model fits because ___.'
Where it leads
Next: Year 9 energy (conservation and efficiency).
In class: a short debate about which model explains a mystery phenomenon; ask students to name another model they have used in science and say what it can't explain.
What each step is for
Engage: who is right?: Students treat a model as true or false. The node asks them to see models as tools with a domain of usefulness.
Explain: where each model works: Sorting phenomena by the model that explains them, explaining a failure, and stating that models are tools meets all three success criteria.
Elaborate: evaluate: Evaluating both models against one phenomenon makes students weigh strengths and limits, not just match labels.
Elaborate: photons: The photoelectric effect is the standard case where the wave model of light alone fails; naming the evidence helps students see why models change.
Now you can
Say which model explains each phenomenon best.
Say where a model stops working.
Explain why models are tools, not copies of reality.