Oobleck non-Newtonian fluid lab
01 // Question
How does cornstarch-to-water ratio relate to a marble's sink depth after five seconds?
Test three measured ratios with the same marble and container, keep three readings from each batch, and treat the quick-tap observation as a separate qualitative check.
02 // Variables
Independent
Cornstarch-to-water ratio- 1:1 by volume
- 1.5:1 by volume
- 2:1 by volume
Dependent
Mean marble sink depth after 5 seconds; separate quick-tap observation- Three depths from separate untouched spots in one batch (mm)
- Mean and range of those readings
- Whether one quick tap briefly resists (qualitative)
03 // Hypothesis
IF the ratio of cornstarch to water is increased, THEN the mean five-second sink depth may be smaller in the higher-starch batches, while a quick tap may briefly meet more resistance, BECAUSE a concentrated starch suspension can resist rapid deformation more than slow movement, though the exact readings depend on how the batch is mixed and measured.
04 // Procedure
1. Measure three equal recipes
Prepare 150 mL by volume at each ratio: 75 + 75 mL, 90 + 60 mL, and 100 + 50 mL cornstarch and water.
2. Mix and divide each batch
Use the same mixing time, then place each batch in a matching wide, shallow tray. Mark three separated, untouched spots for the marble readings.
3. Repeat the five-second reading
Gently lower the same clean marble onto one fresh spot. At exactly 5 seconds, measure the distance from the original surface to the marble's lowest point. Repeat at two other untouched spots in that batch.
4. Make one separate quick tap
After the depth readings, tap a separate spot once with the same tool and record only what you observe. Do not punch or throw the mixture.
5. Compare mean and range
Keep all nine depths, calculate the three-reading mean and range for each batch, and note that repeated spots share one batch rather than representing independent recipe batches.
Materials // Prepare the bench
- Cornstarch and water measured by volume: 75 + 75 mL, 90 + 60 mL, and 100 + 50 mL
- Three matching wide shallow trays
- Same clean marble, ruler with millimeters, timer, labels and stirring spoon
- Covered work surface, scraper and waste container; optional food coloring
05 // Data table
| Cornstarch : water ratio | Spot 1 depth (mm) | Spot 2 depth (mm) | Spot 3 depth (mm) | Mean / range (mm) | Separate quick tap |
|---|---|---|---|---|---|
| 1 : 1 | ____ | ____ | ____ | ____ / ____ | ____ |
| 1.5 : 1 | ____ | ____ | ____ | ____ / ____ | ____ |
| 2 : 1 | ____ | ____ | ____ | ____ / ____ | ____ |
06 // What to expect
A gentle marble placement probes slow deformation, while a separate quick tap probes a faster response. A concentrated cornstarch suspension can resist rapid deformation; it does not become a new solid substance.
Compare the three raw five-second depths, their mean and range, and the separate tap note. A lower mean at a higher starch ratio is one possible pattern, not a guaranteed result; repeated spots from one batch are not independent recipe batches.
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
A concentrated suspension can resist rapid deformation. It remains a mixture, and its response depends on recipe and motion.
09 // Prepare and measure three ratios fairly
Oobleck is a suspension of solid cornstarch particles in water, not a solution or a material that permanently changes from liquid to solid. Compare three volume ratios: 1:1, 1.5:1 and 2:1 cornstarch to water. For each 150 mL ingredient-volume batch, measure 75 + 75 mL, 90 + 60 mL, or 100 + 50 mL. Use the same measuring method, tray shape, mixing time and marble each time. Ratios are recipe labels; packing, moisture and measuring technique can shift the actual concentration.
For each batch, mark three separated spots that have not been disturbed. Gently lower the same clean marble onto the first spot and start a five-second timer at contact. Measure vertically from the original surface to the marble's lowest point at exactly five seconds. Retrieve the marble, move to the next untouched spot, and repeat twice. Keep all nine raw values; calculate the mean and range for the three readings in each batch. These are repeated spots within one batch, not independent recipe batches, so use a second full preparation per ratio if you need stronger evidence.
10 // Separate slow sinking from quick force
The marble test is a practical classroom proxy for how a particular mixture yields under a slow load; it does not directly measure viscosity or establish a universal ratio threshold. After all depth readings, use a separate spot and one quick tap with the same tool. Record a brief observation such as “surface resisted,” “surface yielded,” or “unclear.” Do not call a single tap a calibrated force test. A concentrated suspension can shear-thicken as the rate of deformation rises, while the exact response depends on recipe, mixing, depth and the tool's motion.
Compare means and ranges, not only the largest or smallest reading. If ranges overlap, the marble bottoms out, or spots differ widely, say the batch comparison is inconclusive and name the limitation. The quick tap and slow marble depth are distinct observations; one does not substitute for the other. A follow-up with independently mixed batches or a standardized motion tool can improve the evidence.
11 // Keep the investigation safe and manageable
Use a tray to contain spills and avoid sending cornstarch powder into the air. Do not pour thick slurry into a sink; it can settle and clog plumbing. Let the mixture dry or scrape it into solid waste according to local classroom rules. Keep it away from eyes and mouths, and wash hands after the activity.
For stronger evidence, prepare three separate batches of each ratio and compare their batch means; do not treat several spots in one bowl as independent recipes. Another extension can compare slow and fast tool movement while keeping mixture ratio fixed. Conclusions should name the recipe and motion conditions; saying only that “oobleck is both solid and liquid” hides the useful point that its response depends on deformation rate and test conditions.
12 // Describe what the test can and cannot show
A cornstarch suspension can resist a sudden force more than a slow one, which is why it may feel firm when struck and flow when handled gently. This shear-thickening response depends on the mixture, the rate and type of force, and how the particles are packed. A marble-sink test is only one operational measure of flow; it does not directly measure viscosity unless the method and conditions are calibrated.
Use the same container, marble, release height, and timing rule for each mixture. Let air bubbles settle, avoid stirring at different speeds immediately before a trial, and repeat each ratio. Start with small additions of water because a small change can move the mixture from crumbly to runny. Do not pour cornstarch slurry down a sink: let solids settle, scrape them into the trash, and wipe the remaining residue as directed.
13 // Record the recipe and the timing rule together
A ratio is meaningful only when its parts and measuring method are named. This activity compares ingredient volumes of 75:75 mL, 90:60 mL, and 100:50 mL cornstarch to water in equal 150 mL batches. Measure the same way each time, mix for the same interval, and record whether the batch was unusually dry, wet, or lumpy before the marble test.
For each untouched spot, start the five-second interval when the same marble contacts the surface and measure its depth from the original surface. The three spots describe variation within one prepared batch; they are not three independent recipe preparations. If a claim needs to generalize beyond one mixing, prepare separate batches for each ratio and compare those batch results as well. Never pour the settled slurry into a drain.
14 // Questions people ask
Why can oobleck resist a quick tap but yield under a slow load?
Oobleck is a non-Newtonian suspension whose response depends on deformation rate and recipe. A concentrated cornstarch mixture can resist rapid deformation as particles crowd and jam temporarily, while slower movement lets it yield. It remains a mixture rather than becoming a new solid substance.
What makes a fluid non-Newtonian?
A Newtonian fluid such as water has a stable viscosity under ordinary flow conditions. A non-Newtonian material's apparent resistance changes with the rate or type of deformation. Oobleck is shear thickening over the conditions of this demonstration; other non-Newtonian materials can behave differently.
Why keep three marble readings from one batch?
Separate untouched spots show how much readings vary within that prepared batch. They help summarize that batch, but they are not three independently mixed batches, so repeat the whole recipe in a follow-up before generalizing.
Does this marble test measure viscosity?
No. It is a classroom proxy for how one prepared mixture yields under a slow load. It is not calibrated rheometry, and the result depends on the marble, tray, depth, timing and mixture preparation.
15 // Keep going
Can you explain the investigation?
Oobleck non-Newtonian fluid lab · Student Data Sheet
Question: How does cornstarch-to-water ratio relate to a marble's sink depth after five seconds?
Hypothesis: If the ratio of cornstarch to water is increased, then the mean five-second sink depth may be smaller in the higher-starch batches, while a quick tap may briefly meet more resistance, because a concentrated starch suspension can resist rapid deformation more than slow movement, though the exact readings depend on how the batch is mixed and measured.
Materials
- Cornstarch and water measured by volume: 75 + 75 mL, 90 + 60 mL, and 100 + 50 mL
- Three matching wide shallow trays
- Same clean marble, ruler with millimeters, timer, labels and stirring spoon
- Covered work surface, scraper and waste container; optional food coloring
Safety before starting
- Avoid dry starch dust and do not eat the mixture. Mix over a tray; wash hands after handling.
- Never drain it; let it dry and put the solid in trash. Wipe spills promptly to prevent slips.
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.
Variables
Independent: Cornstarch-to-water ratio · Dependent: Mean marble sink depth after 5 seconds; separate quick-tap observation
Keep constant: same 150 mL batch size and ingredient measuring method · same wide tray and mixture depth · same clean marble · same gentle release and 5-second timer · separate untouched measurement spots
Procedure
- Measure three equal recipes: Prepare 150 mL by volume at each ratio: 75 + 75 mL, 90 + 60 mL, and 100 + 50 mL cornstarch and water.
- Mix and divide each batch: Use the same mixing time, then place each batch in a matching wide, shallow tray. Mark three separated, untouched spots for the marble readings.
- Repeat the five-second reading: Gently lower the same clean marble onto one fresh spot. At exactly 5 seconds, measure the distance from the original surface to the marble's lowest point. Repeat at two other untouched spots in that batch.
- Make one separate quick tap: After the depth readings, tap a separate spot once with the same tool and record only what you observe. Do not punch or throw the mixture.
- Compare mean and range: Keep all nine depths, calculate the three-reading mean and range for each batch, and note that repeated spots share one batch rather than representing independent recipe batches.
Record your observations
| Cornstarch : water ratio | Spot 1 depth (mm) | Spot 2 depth (mm) | Spot 3 depth (mm) | Mean / range (mm) | Separate quick tap |
|---|---|---|---|---|---|
Answer key and expected pattern
A gentle marble placement probes slow deformation, while a separate quick tap probes a faster response. A concentrated cornstarch suspension can resist rapid deformation; it does not become a new solid substance.
Compare the three raw five-second depths, their mean and range, and the separate tap note. A lower mean at a higher starch ratio is one possible pattern, not a guaranteed result; repeated spots from one batch are not independent recipe batches.
Remember: A concentrated suspension can resist rapid deformation. It remains a mixture, and its response depends on recipe and motion.