Density column
01 // Question
Where will an object settle in a column of liquids stacked by density?
An object settles at the boundary where the liquid below it is denser, and the liquid above it is less dense.
02 // Variables
Independent
Object dropped into the column- Grape
- Bottle cap
- Rubber eraser
- Plastic bead
Dependent
Layer the object settles in- Layer name, by liquid
- Matches the prediction? yes/no
03 // Hypothesis
IF an object's density falls between two liquid layers, THEN it will float right at the boundary between them, BECAUSE it is denser than the liquid above it, but less dense than the liquid below it.
04 // Procedure
1. Pour the densest liquid first
Pour honey or corn syrup into a tall, clear container.
2. Add each layer slowly
Pour dish soap, then water (colored), then oil, one at a time down the side or over a spoon.
3. Let it settle
Wait a few minutes for the layers to separate cleanly with sharp boundaries.
4. Predict, then drop
For each object, predict which layer it will stop in, then drop it in and watch.
5. Record the result
Note which layer each object actually settled in and whether it matched your prediction.
05 // Data table
| Object | Predicted layer | Actual layer | Matched? |
|---|---|---|---|
| Grape | ____ | ____ | ____ |
| Bottle cap | ____ | ____ | ____ |
| Eraser | ____ | ____ | ____ |
| Plastic bead | ____ | ____ | ____ |
Formula An object floats at the boundary where the liquid below it has a higher density and the liquid above it has a lower density
06 // What to expect
Each object stops falling once it reaches a layer denser than itself, then floats right at that boundary since it is too light to sink further but too heavy to float up into the layer above.
Pouring too fast mixes the layers together, so the column has to be built slowly — pouring each liquid over the back of a spoon held just above the surface keeps the layers from blending.
07 // Lab notes
- Add a drop of food coloring to the water layer so it is easy to tell apart from the clear layers next to it.
- Pour each new liquid slowly down the inside wall of the container, or over the back of a spoon, to avoid disturbing the layers below.
- Dry each object before dropping it in, since surface water can trap air bubbles that make it float higher than its density predicts.
- Safety. This lab uses only kitchen liquids and food-safe items — low hazard, but avoid tasting anything once layers are mixed.
08 // Remember
Density order is fixed for every liquid. Pour the layers slow, or they mix and the order disappears.
09 // Questions people ask
What order should the liquids be poured in for a density column?
Pour from densest to least dense: honey or corn syrup first, then dish soap, then colored water, then vegetable oil, and finally rubbing alcohol on top if you are using it. Pouring in the wrong order causes the layers to mix instead of stack.
Why does an object stop in the middle of the column instead of sinking to the bottom?
An object settles wherever its own density falls between the density of the liquid above it and the liquid below it — it sinks through every layer that is less dense than itself, and stops the moment it reaches a layer that is denser.
Why do the liquid layers mix if poured too quickly?
Pouring quickly creates turbulence that pushes liquid down into layers below it before the density difference has a chance to separate them again, blurring the sharp boundaries the column depends on.