Too Small to See
A 60-minute Grade 5 lesson on developing a model that describes matter as particles too small to be seen.
Too Small to See is a free 60-minute Grade 5 science lesson plan for Common Core standard 5-PS1-1 — model matter as particles far too small to see. It is timed across 5 sections, gives the exact wording to use where the wording carries the mathematics, names 3 misconceptions with the teaching move that addresses each, and ends with an exit ticket and a printable worksheet with its answer key.
- Grade:
- Grade 5
- Length:
- 60 minutes
- Standard:
- 5-PS1-1
Grade 5 · Physical Science
5-PS1-1
Develop a model to describe that matter is made of particles too small to be seen.
Objective
Students will be able to use a particle model to explain an observation they cannot see the cause of.
Students are successful when they can
- Explains dissolving using particles.
- Gives evidence the substance is still present.
- Says what the model predicts as well as what it explains.
What you need
- Sugar, water, beakers, a balance, evaporating dishes
- A bottle of scent for a diffusion demonstration
- The printable practice sheet linked at the end of this plan
The lesson
Warm-up
5 min- Stir sugar into water until it vanishes and ask where it went.
- Take every answer, including 'it disappeared'.
Teach — a model you cannot see
15 min- Weigh the beaker before and after dissolving: unchanged.
- Ask what that rules out. That the sugar was destroyed.
- Taste it, or evaporate a spoonful and show the sugar returning.
- State the model: the sugar broke into particles too small to see, spread through the water.
- Open the scent bottle at the front and time how long until the back row smells it.
- Say what makes it a good model: it explains this AND predicts the scent result.
“You cannot see it. What can you measure instead?”
Investigate — three observations, one model
22 min- Groups dissolve a weighed sample and reweigh the sealed container.
- They evaporate a portion and recover the solid.
- They time a smell crossing the room.
- They write one sentence explaining all three with the same model.
Independent practice
15 min- Students complete the 'Too Small to See' page.
- Check answers use the model rather than repeating the observation.
Close
3 min- Ask what observation the model would struggle to explain.
What goes wrong, and why
Each of these is a reasoning error rather than carelessness. The fix addresses the reasoning.
Says the sugar turned into water.
Why: It looks like water afterwards.
Fix: Evaporate it. The sugar comes back and the water does not.
Thinks a model is only useful if you can see what it describes.
Why: Seeing is believing.
Fix: Nobody has seen a particle here. The model earns its place by predicting.
Says the sugar was destroyed.
Why: It vanished from view.
Fix: The mass did not change. Destroyed matter would weigh less.
If they are not there yet
- The dissolving and reweighing only.
- A model sentence with a gap to complete.
If they finish early
- Explain why a smell reaches the back row later than the front.
- Predict what happens if the water is warmed first, then test it.
- Say what the model does not explain.
Exit ticket
Sugar dissolves and disappears from view, but the sealed jar weighs the same. Explain both with one model.
What to look for: The sugar broke into particles too small to see and is still present, so the mass is unchanged. 'It disappeared' means the model is not being used.
Printable practice for 5-PS1-1
Free to print and copy, answer key included. Each sheet can generate a fresh set of problems for a retake.
- Too Small to SeeCircle the best answer.
Questions about Too Small to See
How long does the Too Small to See lesson take?
60 minutes, split across 5 timed sections: warm-up 5 min, teach 15 min, investigate 22 min, independent practice 15 min, close 3 min. The minutes are stated per section and add up to the stated length, so the plan can be cut or extended at a section boundary rather than abandoned halfway.
Which standard does Too Small to See teach?
5-PS1-1 — 5-PS1-1, Physical Science for Grade 5: “Develop a model to describe that matter is made of particles too small to be seen.” In plain terms, model matter as particles far too small to see.
What do I need to teach this lesson?
Sugar, water, beakers, a balance, evaporating dishes, a bottle of scent for a diffusion demonstration and the printable practice sheet linked at the end of this plan. Everything listed is either ordinary classroom equipment or a free printable from this site — there is nothing to buy and nothing to prepare beyond photocopying.
What mistakes should I expect in this lesson?
Three, each a reasoning error rather than carelessness: says the sugar turned into water; thinks a model is only useful if you can see what it describes and says the sugar was destroyed. The plan gives the thinking behind each one and the teaching move that addresses the thinking rather than the symptom.
How do I know whether the lesson worked?
The exit ticket asks: “Sugar dissolves and disappears from view, but the sealed jar weighs the same. Explain both with one model.” The sugar broke into particles too small to see and is still present, so the mass is unchanged. 'It disappeared' means the model is not being used. That tells you whether the class needs a reteach or a thirty-second conversation before you plan tomorrow.
Is there a worksheet to go with Too Small to See?
Yes — 1 printable 5-PS1-1 worksheet, linked at the end of the plan and free like the rest of the site. Each one comes with an answer key and 25 versions, so the practice after the lesson can be a different paper on every desk.
Is Too Small to See free to use?
Yes. The plan, its printables and their answer keys are free to read, print and photocopy for your own class, with no account and no email capture. It was last reviewed on 8 September 2026. Please do not resell it or republish it as your own.
Last reviewed 2026-09-08. Aligned to 5-PS1-1 of the Next Generation Science Standards.