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Scientists describe all matter on Earth as having constant molecule motion. Molecules in a gas are moving rapidly. Molecules in a liquid move quickly but not as fast as a gas. The molecules in a solid typically vibrate in place.

Using a microscope, you will should be able to observe random motion as you do this activity. If you do not know how to use a microscope correctly, please ask a teacher or responsible adult to assist you. Your success in this activity depends on your eyes being able to stare. Perhaps the staring contest you did with friends will help you now!

Materials:

  • Microscope
  • Microscope slide
  • Cover slip
  • Two percent milk
  • Eye-Dropper

Directions:

  1. Place a drop of milk on a microscope slide.
  2. Add a cover slip.
  3. Place the slide on the microscope stage and focus using low power. (Focus on a "fat globule".)
  4. Adjust the microscope lens to medium power.
  5. Observe the "fat globule" through the microscope.
    • Pick a fat globule and stare.
    • Look for the motion of the fat globules in two-percent milk. (This motion is called Brownian motion. The fat globules move because of the motion of the molecules in the milk. Even though you are unable to see the milk molecules moving, you can see the results of their motion.)

Safety concerns: icon icon Be sure to follow all chemical and glassware safety rules that are specified by your teacher in all general laboratory experiences. Remember not to put a stopper into any flask unless given direct instruction by your teacher. Handle the microscope with care.

Analysis

  1. Draw what a fat globule looks like as seen through a microscope.
  2. Diagram the motion of a single fat globule as observed through the microscope.
  3. Does the motion of the fat globule change as it is over the microscope lamp?

Review science lab safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share a photograph of you or your friends doing this activity? Send the photograph attached to an e-mail with the following information: the title of the activity, the URL (Internet address), and your name. Remember that no pictures can be used which show any student faces or has a student name on it.

Updated August 11, 2005 by: Glen Westbroek

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