1. HOMEWORK DUE TOMORROW 10-24-12 Water Molecules 4 questions You may need to use the internet !

2. HOMEWORK STICKY WATER LAB 1. Utilize the terms adhesion, cohesion, polarity, and surface tension to your explanation of the following questions. Use complete sentences. 2. Explain why the drops of water were able to remain on the penny and seemed to “defy gravity”. 3. Explain how the paper clips were able to “float” on the water. 4. Relate the activities from class today to the movement and habits of the water strider. 5. Predict what would happen to the water chemistry of the surface of a stream, pond, lake, etc., if pollutants were added to the water. What might happen to the critters that live on the surface ?

3. 1. Explain why the drops of water were able to remain on the penny and seemed to “defy gravity”. Water as a molecule is neutral Because of its structure, it is polar Polarity makes it attracted to water molecules and the molecules of other substances The attraction between water molecules is called cohesion.

5. 2.Explain how the paper clips were able to “float” on the water.. The attraction of water molecules to other substances, like soil or glass, is called adhesion. The cohesive force that occurs between water molecules is so strong that when comes in contact with another medium, such as air, the water creates a "sticky skin", which is known as surface tension.

6. 3.Water Strider and Whirligig…. These bonds are so strong that they can support insects.

7. Adhesion or Cohesion?

9. Adhesion Cohesion Surface Tension Video

10. What happens when pollutants enter the water? Compare your results with “clean water” to the number of drops you were able to place on the penny with “polluted water”. Is soap a reasonable Pollutant??