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Vacuum Demonstrations

One of the most important concepts in understanding the operation of the early steam engines is the creation of vacuum by condensation. These demonstrations provide simple illustrations using a soft drink bottle and boiling water.

The important thing to recognize is that condensation can pull a vacuum. The vacuum can be substantial if all the air is removed from the vessel before condensation. If air is completely removed and the vapor is condensed, the final pressure will be the vapor pressure of water. At 25C, this is 0.032 bar, 24 mm Hg, or 29.0 inches of vacuum!

The demos on this page are in QuickTime format, version 4.0 or greater. You need only the free version of QuickTime software available from this link. Each demonstration is furnished in different levels of compression that can be selected based on your connection speed.

Experiment Setup

The setup consists of a pot of colored water on the left. The pot is not heated. The pan on the right holds colored water that is boiling during experiments where the bottle is heated.

Demo using dry bottle without heating.

  • The selected movie will open in new window. Close the new window to return here. (All movies are from the same original, but vary in compression)
    28.8k Modem (0.23 MB)
    56k Modem (0.4 MB)
    ISDN (0.9 MB)
    T1 (1.5 MB)
  • The photo on the left is at the end of the demo.

This demo shows an inverted bottle being submerged in colored water. The air keeps the colored water from entering the inverted bottle and verifies that water will not spontaneously enter. You may want to skip this one if you understand that concept.

Demo using dry bottle.

  • The selected movie will open in new window. Close the new window to return here. (All movies are from the same original, but vary in compression)
    28.8k Modem (0.64 MB)
    56k Modem (1.1 MB)
    ISDN (2.5 MB)
    T1 (4.2 MB)
  • The photo on the left is at the end of the demo.

Demo using water in bottle

  • The selected movie will open in new window. Close the new window to return here. (All movies are from the same original, but vary in compression)
    28.8k Modem (0.68 MB)
    56k Modem (1.2 MB)
    ISDN (2.7 MB)
    T1 (4.5 MB)
  • The photo at left is at the end of the demo.

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Updated 11/22/12 ,Copyright 2001, Carl T. Lira, lira@egr.msu.edu All rights reserved.
Prepared as a supplement to Introductory Chemical Engineering Thermodynamics.