All lessons › Oobleck: test an unusual mixture › Lesson 1
Australian primary science · Years 5–6 · Lesson 1 of 1
Oobleck: does movement speed matter?
Inquiry question: Does oobleck resist a spoon differently when we move it slowly and quickly?
Check practical materials
Fair testing
What students learn
Compare how the same oobleck suspension flows or resists under slow and faster movement, use repeated evidence, and explain why this is not a change of state.
Success criteria
- I can identify movement speed as the factor we intend to change and name at least three things we will try to keep the same.
- I can compare slow and faster movements three times, recording what I felt or saw instead of guessing.
- I can support a conclusion with at least two observations and explain a limitation of our test.
Preparation and materials
Before this lesson: Students have described materials using observable properties and can identify a factor to change and some factors to keep the same.
- Cornflour (cornstarch) — 13 cups for 13 pairs (1 cup per pair), plus extra for adjustments
- Water — 6.5 cups for 13 pairs (about 1/2 cup per pair), plus handwashing water
- Small bowls on washable trays — 13 sets
- Plastic spoons (same spoon for both speeds) — 13
- 1-cup and 1/2-cup measures — 13 sets, or teacher-portioned ingredients
- Timer or teacher counting cue — One classroom display; no student device needed
- Paper towel and cleaning cloths — As needed
- Food colouring (optional) — A few drops; omit where staining is a concern
Teacher setup
- Check school allergy, skin and sensory requirements; arrange a non-contact observer/recorder role for any student who does not handle the mixture.
- Teacher portions dry cornflour to avoid airborne powder. Put a bowl and plastic spoon on each pair's tray.
- Pre-agree a gentle, repeatable push depth and spoon angle. Demonstrate timing and the rating scale on water only.
- Prepare a six-row table: Try 1 slow/quick, Try 2 slow/quick and Try 3 slow/quick. Explain a rating: 0 = moved easily; 1 = slight resistance; 2 = strong resistance. A rating is an estimate, not a force measurement.
- Have one labelled student record per student or a shared pair table plus each student's own short science explanation. Printer needed only if pupils are not copying the table into books or using iPads.
Safety and adaptations
- Do not taste the mixture or touch eyes/mouth; wash hands after the activity.
- Avoid breathing cornflour dust; teacher portions the dry powder. Check allergies and sensory accommodations.
- Push gently with a plastic spoon. Do not punch, strike, splash or force the spoon toward anyone.
- Wipe spills straight away and keep all oobleck out of sinks and drains.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Before mixing, write a hypothesis predicting which spoon movement will meet more resistance. Identify speed as the intended changed factor. Name what you will keep the same: spoon, mixture, depth and angle.
- Teacher provides 1 cup cornflour per pair. Mix in up to about 1/2 cup water slowly; stop once the mixture flows when moved gently but offers some resistance to a quick gentle push. Record any adjustments BEFORE trials.
- With the same plastic spoon and bowl, slowly push the spoon into the mixture to the agreed depth over about 3 seconds. Note what happened and rate resistance 0 (easy), 1 (slight), or 2 (strong).
- Lift the spoon, let the mixture settle, and push the SAME spoon to the SAME depth over about 1 second. Do not strike or splash. Record the observation and rating.
- Repeat the slow/quick pair TWO more times using the same bowl, spoon, angle and depth. Do not add water during trials; tell the teacher if the mixture changes.
- Compare the six entries. Does the quicker movement usually meet more resistance? Support your conclusion with two named results and state one limitation of the rating method.
Teacher modelling prompt
Draw TWO labelled diagrams: water with many tiny cornflour particles for slow movement, and a closer, crowded particle arrangement for faster movement. Label the drawings 'model, not observed directly'. Explain that the mixture's resistance can increase temporarily when particles interact under faster movement; this is not particles turning into a new solid or a chemical reaction. Teacher shows a slow/quick water-only example of the procedure, not an oobleck answer.
Record and explain evidence
Recording question: Does oobleck resist a spoon differently when we move it slowly and quickly?
| Try and movement | What I saw or felt | Resistance 0 / 1 / 2 |
|---|---|---|
| ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which claim fits our six observations? Why are the others too strong?
Check understanding
What should pupils know? What is a suspension, and which ingredients make up our oobleck?
Explain with evidence: Your slow and quick scores differed in two tries but matched in one. What can you conclude, and what should you check before claiming speed caused the difference?
Apply the idea: A classmate says the oobleck became a solid because the spoon met resistance. Use TWO different observations to respond.
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.