Student activity with a simple centrifuge

by Stephanie Chasteen on October 18, 2009

Got a unit on circular motion? You may want to use an activity with a centrifuge, to show how it separates substances of different densities. Even if you’ve got a commercial centrifuge, how might you instead do a hands-on activity to show the same thing?

Try mixing red colored sugar in cooking oil in a syringe (10 ml). You can use the holiday colored sugar, or dye your own with food coloring. Attach string to the syringe (very securely!) and swing it around your head. This simulates a hematocrit test, which measures blood count, and the mixture looks a little bit like real blood. The sugar represents the packed cells, and the oil is the color of plasma.

Thanks to Karen Kalumuck of the Exploratorium for this idea. If you want a copy of her write-up of the activity, write me (stephanie at sciencegeekgirl dot com).

Another low-tech centrifuge is a salad spinner, which you can get at any thrift shop.  Separating vegetables from water is not quite a density-driven process, as the vegetables are large and the water is driven to the outside because of its fluidity.  Though, you will find that carrots end up on the outside and lettuce on the inside.


Michael Varney October 18, 2009 at 11:43 pm

Another interesting density driven process to play with is to take a cup of dried rice, and add to it 10-20 dried pinto beans.
Put the beans in the bottom of a bowl, and put the rice over the beans.
Then shake the bowl back and forth gently.
You will notice the dried pinto beans rise to the top.

This is also a quick and easy way to get the last few nuts out of the detritus and crushed nuts in a nearly empty can of mixed nuts!

Rounak bhardwaj July 1, 2013 at 11:07 am

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