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Fluids Experiment: Compare the Density of Different Liquids

by Ron Kurtus (updated 21 November 2022)

You may have noticed that when you combine to liquids that don't readily mix that one will float to the top. One example is mixing oil and water. The reason that one floats to the top is that it has less density than the liquid on the bottom. This may get you curious as to what the density of each liquid is. Knowing that you will allow you to predict which one will float on top of the other.

Finding the densities can be an idea for a science project in the area of Physical Science. Also, this is a demonstration that can be a good exercise in scientific procedures. Since density is mass divided by volume, you simply need to weigh a defined volume of the liquid and make your calculations.

Questions you may have include:

This lesson will answer those questions.

Purpose of experiment

The purpose of this experiment is to measure the densities of several liquids and then predict which one will float on top of the other. Note that the liquids must not be ones that dissolve into each other.

Research and factors

Not much research is required for this experiment, since it is a demonstration. You could do some preliminary examinations to see which liquids do not mix into solutions.


Select materials and then follow the procedure.



  1. Weigh each of the similar beakers.
  2. Pour an equal volume of oil and water into two separate beakers.
  3. Weigh each beaker with its liquid.
  4. Determine the density of each liquid.
  5. Pour the lower density liquid into the third beaker.
  6. Pour the higher density liquid into the beaker.
  7. Observe what happens.

Keep records

If this is going to be an experiment for a science fair, you will need to record your activities in a log book.

Draw conclusions

You can draw conclusions about the relationship between density and floating.

Write report

Write up a report to summarize your results and your proposed solution to the problem.


You can find the densities of various liquids and show which ones will float on the other. This is a demonstration that can be a good exercise in scientific procedures.

Have good character

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