Easy Science Experiments
Pumice & Obsidian

These easy science experiments look at the difference between pumice and obsidian. Even though pumice and obsidian look very different they are made from the same igneous rock material. They are also both glassy rocks.

Pumice is a froth of igneous rocks that has so many gas bubbles it can float. There are reports that after the eruption of Krakatoa that some pumice formed rafts and floated for over 20 years before they sank. Approximately 90% of the rock will be gas bubble holes making it very light.

Easy Science Experiments, Pumice & Obsidian, Photo by Myrna MartinEgg whites show difference between pumice and obsidian

Obsidian is a volcanic glass that is between 70% and 75% quartz. It forms lava flows that ooze out of the ground. Even though there are large lava flows of this rock the lava does not crystallize. Some scientists believe it is because of its low moisture content that is about 1%.

Most obsidian is black and resembles basalt. It forms mainly from rhyolite a lava rich in quartz. Rhyolite is a light colored lava. The dark color of obsidian is due to impurities in the rock. In this science experiment you will use egg whites to see the relationship between obsidian and pumice.


  • Six eggs
  • Mixer
  • Two bowls
  • Mixing bowl
  • Spatula
  • Measuring cup
  • Paper and pencil


  1. Break and separate the whites from the yolks of three eggs.
  2. Place the whites of the three eggs in one bowl.
  3. Break and separate the remaining three eggs into yolks and whites.
  4. Place these three egg whites in a measuring cup.
  5. Measure the amount of liquid in the whites and put them in a mixing bowl.
  6. Measure the amount of liquid in the whites of the eggs in the first bowl.
  7. Record the information on a sheet of paper.
  8. Make prediction how much the egg whites in the mixing bowl will increase in volume when you whip them.
  9. Write your prediction down on the paper also.
  10. Whip the egg whites in the bowl until they form peaks when the beaters are lifted out of the bowl.
  11. Using your spatula scrape the egg whites out of the mixing bowl and into the measuring cup.
  12. After measuring the amount of volume in the whipped egg whites compare that to the volume in the other bowl.
  13. Decide if you proved your prediction.

More Links to Science Experiments

Volcano Science Experiment, Cinder Cones Have you ever wondered how volcanoes get their shape? Find out about cinder cones in this fun activity.

Gravity Experiments, Balancing Acts Learn how to balance a potato, fork and pencil on the edge of a table.

Elementary Science Experiment, Earthquake Waves Create your own wave box that makes paper clips jump when earthquake waves pass through them.

Gravity Experiment, Topsy Turvy Plants Have fun growing tomatoes upside down in this fun experiment.

Elementary Science Experiments, Bird Feeders Study the feeding habits of wild birds in your back yard or porch area in this interesting experiment.

Easy Science Experiments, Pumice & Obsidian Find out the difference between pumice and obsidian and why one will float and the other will sink like a rock in these easy science experiments.

Earth Science The links on this page include information on the Earth, the Rock Cycle, Volcanoes, experiments, activities and much more.


RC Igneous Rocks
ID Metamorphic Rocks

Check out Myrna Martin's award winning textbooks, e-books, videos and rock sets.  The Kids Fun Science Bookstore covers a wide range of earth science topics.  Click here to browse. 

Share this page:
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.

Sign up to our monthly newsletter and receive our FREE eBook containing 3 fun activities that don’t appear in any of our other books!

The Kids Fun Science monthly newsletter will include the following: current events, weird and fantastic facts, a question of the month, science trivia and the latest new content from our website.

We respect your privacy and you can be assured that we will never share your email address or use it for any other purpose than to send you our newsletter.