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# Bond Polarity

## Use electronegativity values to determine bond type

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The Lotus Effect

### The Lotus Effect

Credit: The_Gut
Source: http://www.flickr.com/photos/frogbelly/3851056758/

Commercials for waterproofing sprays commonly show water and other water-based liquids, such as wine, mud, or chocolate sauce, being poured onto a treated surface. Instead of sticking to the surface, the liquid beads up and rolls off. Although the commercials may try to convince you that their product is a futuristic, space-age technology, certain plants have been using this same principle, sometimes referred to as the lotus effect, for millions of years to keep their leaves clean and dry.

#### News You Can Use

• The lotus effect can be observed when a nonpolar material forms a thin protective film on a surface. It is more energetically favorable for polar water molecules to cluster together than to spread out over a nonpolar surface, so water-based liquids will bead up instead of soaking through.
• Credit: Brett Taylor
Source: http://www.flickr.com/photos/glutnix/5571240/

Water beads on the surface of a rain jacket instead of soaking through [Figure2]

• A smooth hydrophobic surface would provide some protection, but an especially water-repellent surface can be generated if the nonpolar coating is very rough at the molecular level.
• Watch demonstrations of the lotus effect in the following videos:

#### Explore More

1. Explain how the lotus effect helps keep surfaces clean.
2. The higher the surface tension of a liquid, the more likely it is to bead up and form droplets on a very rough surface. Explain this phenomenon.
3. Based on the surface tension values found in the links above, what are some other liquids that would also be repelled by the lotus effect?
4. What trends can be found regarding the intermolecular interactions in various molecular liquids that exhibit high surface tension? (Note: Ignore mercury, which is not a molecular liquid.)

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