Density column in a jar: a 40-minute middle school lab
What it is: students layer five household liquids in a clear jar, predict the order before pouring, then test small objects to see where each one stops. It turns the idea of density (how much mass is packed into a given volume) into something students can see. Suited to grades 6–8.
Time: about 40 minutes, including cleanup.
Materials per group: a tall clear jar or cup, honey, dish soap, water with a drop of food coloring, vegetable oil, rubbing alcohol with a different food coloring, a spoon, and small test objects such as a grape, a plastic bead, a small piece of cork and a coin. Safety goggles. Rubbing alcohol is flammable and must not be swallowed: keep it away from any flame and have an adult pour or supervise it.
- Show the five liquids. Each student writes a prediction of the order from bottom to top and a reason.
- Pour about the same amount of each liquid in this order: honey, dish soap, colored water, oil, colored alcohol. Pour slowly down the inside of the jar or over the back of a spoon so the layers don't mix.
- Compare the result with the predictions. In most kitchens the order from bottom to top will be honey, dish soap, water, oil, alcohol, because each liquid is less dense than the one below it.
- Before dropping each object in, students predict which layer it will stop in. Drop the objects one at a time and record what happens.
- Discuss: an object sinks through a liquid that is less dense than it and floats on one that is more dense.
- Exit ticket: "Why did the oil stay on top of the water even though we poured the oil in after the water?"
What to change next time: advanced groups can measure 50 mL of each liquid on a kitchen scale and calculate density as mass divided by volume. For students who need support, use only three liquids (honey, water, oil) and two objects, and give a sentence frame: "The ___ floated on the ___ because ___."
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About this resource
- Shared by
- @UpOnlyLearning · Curriculum team
- Posted
- Oct 27, 2026
- Type
- Lesson plan
- Grade
- Grades 6–8
- Subject
- Science
- Language
- English
- License
- Free for classroom, co-op and tutoring use. Please don't resell.