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Centrifuge

based on 2 ratings
Author: Crystal Beran

Grade Level: 7th - 10th; Type: Physics

Objective:

To find out what common “compounds” can be easily separated out in a centrifuge.

The purpose of this experiment is to find out whether certain liquids are comprised of a liquid and a dissolved solid or two different liquids of different densities. Spinning a liquid in a centrifuge will separate materials of different densities from each other but will not be able to separate out materials that have been chemically bonded into the liquid suspension.

Research Questions:

  • How does a centrifuge separate materials from one another?
  • What types of materials can a centrifuge separate out?
  • What types of materials cannot be separated out by a centrifuge?
  • Can a centrifuge separate out materials that have been chemically bonded?
  • Can a centrifuge be used to separate out dissolved solids from a liquid suspension?

The centrifuge is a laboratory tool that has been used for hundreds of years. The first centrifuges were powered by a hand crank which was used to spin the holding compartment or compartments quickly around an axis in the center of the machine. Spinning these materials at high speeds applies a pressure to the materials in the centrifuge equal to many times the force of gravity. With this amount of pressure placed on the materials, the less dense materials quickly “float” to the center of the centrifuge while the denser materials “sink” to the outside of the machine. In this way, liquids that appear to be homogenous can be separated out into their components. The first centrifuges were used to separate cream from milk. Nowadays, electronic centrifuges are used for many applications and are commonly found in medical laboratories to separate blood cells from the plasma in blood.

Materials:

  • A centrifuge
  • Various liquids to separate (examples are below)
  • (optional) salt water
  • (optional) J-ello
  • (optional) wet sand
  • (optional) orange juice
  • (optional) Gatorade
  • (optional) mud
  • (optional) half and half

Most materials can be purchased at a grocery store or made out of materials you find around your house. You will need to borrow a centrifuge from your school’s science lab. Your science teacher may want you to perform your experiment at school as a centrifuge is an expensive piece of equipment. If your school does not have a centrifuge, check with another nearby school or university.

Experimental Procedure:

  1. Gather together the materials you wish to separate out.

  2. Pour each of them (they must be liquids!) into the centrifuge containers.

  3. Label each container with the materials you have placed inside.

  4. Place the containers in the centrifuge. You may want to have a science teacher or other adult with you to help you operate the centrifuge.

  5. Spin the materials at high speed.

  6. Allow the centrifuge to come to a rest.

  7. Take out the containers and record the results on a chart such as the one below.

name of compound
material 1
material 2
Separated out?
separated into material 1
separated into material 2
half and half
half and half
none
yes
cream
milk
Jell-O
Jell-O powder
water

 

 

 

mud
dirt
water

 

 

 

wet sand

 

 

 

 

 

orange juice

 

 

 

 

 

salt water

 

 

 

 

 

 

Terms/Concepts: Centrifuge; Density; Force; Centripetal force

References:

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