Oobleck non-Newtonian fluid lab
01 // Question
How does the ratio of cornstarch to water change how fast a marble sinks into the mixture?
A testable question names one thing you change (the ratio) and one thing you measure (sink time or depth).
02 // Variables
Independent
Cornstarch-to-water ratio- 1:1 by volume
- 1.5:1 by volume
- 2:1 by volume
Dependent
Marble sink behavior- Depth the marble sinks in 5 seconds (mm)
- Whether the marble stays on the surface when tapped
03 // Hypothesis
IF the ratio of cornstarch to water is increased, THEN a marble will sink more slowly into the mixture and resist tapping more, BECAUSE more tightly packed cornstarch particles lock together under sudden pressure, while the same particles still slide past each other under slow, gentle force.
04 // Procedure
1. Measure the ingredients
Measure cornstarch and water in the ratio being tested and combine them in a wide, shallow container.
2. Mix thoroughly
Stir until no dry cornstarch pockets remain, using the same stirring time for every batch.
3. Place the marble gently
Rest a marble gently on the surface and start a timer, recording how far it sinks in 5 seconds.
4. Test a quick tap
Firmly tap or punch the surface once and observe whether it feels solid or splashes like a liquid.
5. Compare ratios
Repeat with a new batch at each ratio and compare both the slow-sink and quick-tap results.
05 // Data table
| Cornstarch : water ratio | Marble depth at 5 s (mm) | Feels solid when tapped? |
|---|---|---|
| 1 : 1 | ____ | ____ |
| 1.5 : 1 | ____ | ____ |
| 2 : 1 | ____ | ____ |
06 // What to expect
A marble placed gently on oobleck sinks slowly, but a fast tap or punch makes the surface feel solid — a hallmark of a non-Newtonian fluid, whose resistance to flow changes depending on how much force is applied to it.
Mixtures with more cornstarch relative to water usually resist a quick tap more strongly and let a resting marble sink more slowly, because there are more tightly packed particles available to jam together the instant sudden pressure is applied.
07 // Lab notes
- Never pour oobleck down a sink drain — let it dry out completely and throw the solid pieces in the trash.
- Work over a covered surface or tray, since oobleck can drip and gets messy quickly.
- This lab uses only cornstarch and water — low hazard, but avoid eating the mixture.
08 // Remember
Most liquids resist force the same way no matter how fast you push. Oobleck doesn't — hit it fast and it fights back like a solid.
09 // Questions people ask
Why does oobleck act like a solid when you punch it but like a liquid when you rest your hand on it?
Oobleck is a non-Newtonian fluid — its resistance to flow depends on how fast force is applied. A sudden, fast force jams the cornstarch particles together before they have time to slide past each other, so it briefly behaves like a solid. Slow, gentle pressure gives the particles time to flow around each other like a liquid.
What makes something a non-Newtonian fluid?
A Newtonian fluid, like water, has the same resistance to flow no matter how much force is applied. A non-Newtonian fluid's resistance changes with the force or speed applied to it — oobleck gets more solid-like under sudden force, while some other non-Newtonian fluids, like paint, actually flow more easily the harder they're stirred.
Why does more cornstarch make oobleck feel more solid when tapped?
A higher ratio of cornstarch to water packs more solid particles into the same space, leaving less water to lubricate the gaps between them. Under a sudden force, those tightly packed particles jam against each other more strongly and resist flowing, producing a firmer, more solid-feeling response.