Surface Tension with Oil and Pepper
Description: Two petri dishes of water are treated with black pepper. One is treated with mineral oil and one with olive oil. The hydrophobicity causes either a minimization or a maximization of surface area exposure to the water. The olive oil spreads the pepper at the water surface, while the mineral oil does not.
Another version is done with soap to form the monolayer. Repeated application reduces the effect.
Another version uses isopropanol, and the IPA will dissolve in water and evaporate, making a different effect.
Source: Nathanson, Gilbert Prof.
Year: 2010 Vol: N/A Page: N/A
Keywords: Surface tension, Thermodynamics, Physical Chemistry, Hydrophobic, Surface area
Rating: 
Hazard: Low
- No appreciable hazards
Effectiveness: Good
- Good connection from demo to course material
- Results are observable without guidance
- Moderate failure rate
- Time to results is low
Difficulty:
- Prior practice or training recommended
- Precise control of contamination
- Some intermediate steps to results
- Some sequential manipulation
Safety Precautions:
- Avoid exposure to open flames during preparation
- Avoid exposure to open flames during performance
- Gloves recommended
- Minimum observation distance is one meter
Class: Intermolecular Forces
Division: General, Physical Chemistry
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