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Ward's World Hydrophobic Effect Activity

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Page 2 Expected Results: When hydrophobic sand is sprinkled on the water's surface, the water molecules bond with other water molecules instead of with the non-polar sand. This prevents the grains of sand from breaking through the surface. The sand appears to stick to the finger when submerged. The sand then stays on the water's surface until enough sand collects to break the surface tension. When large amounts of sand are added, intestinal shapes form at the bottom of the beaker. Follow up: • Explore the effects of detergents on the surface tension of water. • Predict how normal beach sand and hydrophobic sand would behave in methanol (CH3OH). Explain. • Explore how nanotechnology is changing products that we use in everyday life, mostly through surface treatments (like hydrophobic sand). Teaching notes: • The non-polar sand does not mix with the polar water molecules. • The sand appears to bond together in water, giving rise to the concept of hydrophobic bonding. • The effect disappears with ethanol or if regular sand is used in water. Questions and observations for students: 1. Predict what will happen when you put a drop of water on a pile of hydrophobic sand. Explain. 2. Predict what will happen when you put regular beach sand and hydrophobic sand in oil. Explain. 3. How could hydrophobic sand be used to help clean up oil spills in the ocean? 4. Can you think of how mixing some hydrophobic sand in soil can keep plants healthy? 5. Can you find examples of the hydrophobic effect in nature? Disposal/Clean-Up: • Recollect the sand for reuse by filtration. • The used water can be washed down the drain. • The used alcohol can be washed down the drain with lots of water. Fear of Water (continued) + ward ' s science 5100 West Henrietta Road • PO Box 92912 • Rochester, New York 14692-9012 • p: 800 962-2660 • wardsci.com Find materials for this activity at wardsci.com. Discover more free activities at wardsworld.com

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