Molecular Structure, Bonding, Orbital Hybridization
9.1 Bending Water
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Subjects: Bonding, polarity
Description: A stream of water is “bent” upon interaction with a statically charged glass rod.
Materials:
- Glass rod
- Rabbit fur
- Stream of water from faucet in sink (in lecture hall)
- Optional: Vernier Charge sensor (with logger pro or logger lite software and GoLink interface)*
*Located in the drawers opposite the bin storage shelves.
Procedure:
Note: It may be helpful to project this demo using a demo camera
- Charge the rod by rubbing it with the fur.
- Turn on the water faucet.
- Hold the charged rod next to the stream and observe that the stream is attracted to the rod.
- Try it with a balloon – charge with your own hair or have a student do it (balloons in bin 9.0).
Discussion:
Water is a bent triatomic molecule. Because of the larger electronegativity of oxygen, the O-H bonds are polar, with the hydrogen atoms having a partial positive charge and the oxygen atom having a partial negative charge. Electron density accumulates on the oxygen side of the molecule. The partial positive charge of the water is attracted to the build-up of negative charge on the glass rod, “bending” the stream of water towards the rod.
Safety:
None.
Disposal:
None.
References:
1. L. Summerlin, C. Borgford, J. Ealy. Chemical Demonstrations: A Sourcebook for Teachers; 1987; Volume 2; p. 89
