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General Physics Science Fair Project

Measuring Rock Density

Measuring Rock Density | Science Fair Projects | STEM Projects
In this science project, water displacement and triple beam balances are used to calculate the density of rocks. Explore the differences in density among different types of rocks and discover why some rocks are denser than others.


The hypothesis is that different kinds of rocks will have different densities.

Method & Materials

You will use water displacement to find the volume of each rock. Fill a graduated cylinder half-way with water and place it into an overflow can. Put one rock in and note the volume of the water. The difference of the water volume is the volume of the rock. Measure the rock’s mass with a triple beam balance. With the volume and mass of the rock, you can calculate the density of the rock using the formula density = mass/volume.
You will need rocks of different types (approximately 3 cm in width, height, and length), a triple beam balance, a graduated cylinder, an overflow can, and water.


Different kinds of rocks have different densities. Density is determined by the types of material the rocks are made of and how closely they were packed during formation. The volume of irregularly shaped rocks can be accurately measured using water displacement.

Why do this project?

This science project is interesting because it explores the physical properties of rocks and uses water displacement to measure the volume of irregularly shaped objects.

Also Consider

Experiment variations to consider include testing the density of rocks found in different locations or comparing the densities of rocks of different sizes or shapes.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

Related video

Hey there! Here are some awesome videos about this science project that we think you'll really like. They're not only super fun, but they'll also help you learn more about the science behind the project. So sit back, relax, and get ready to have some fun!!
Ever wondered how to measure the density of a rock, regardless of its shape? Using water displacement with a graduated cylinder is a great way to do that! And if the rock is too large, an Eureka can, also known as a density can, can do the trick!
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