1. The Chemistry of Water

2. “When the well’s dry, we know the worth of water”--Benjamin Franklin

3. Water’s polarity results in hydrogen bonding • Water is a polar molecule

4. The charge of the water molecules results in hydrogen bonds

5. Properties: Hydrogen bonding results in… • Cohesion—__________________ • Adhesion—__________________________________________________________ Both responsible for capillary action. • Surface __________________________________________________________

6. Which properties apply here?

7. Property: Water has a high specific heat • Specific heat—amount of energy to cause 1 g of a substance to change its temperature by 1º C. • Water’s specific heat is __________________ • The reason water’s specific heat is high is because a __________________________________________________________

8. Water has a high specific heat • Areas surrounded by water have moderate temperatures—the water absorbs the heat—without raising the temperature of the water. • At night the loss of the heat by water warms the air. • The result—the water itself and the surrounding land have a constant temperature

9. Property: Water results in evaporative cooling • Heat of _______________________________________________________________________________________ • This helps moderate earth’s climate • As a liquid evaporates, the surface of the liquid that remains behind cools down. This is ________________________________.

10. How does evaporative cooling result in • Stability of temperature in lakes and ponds? • A mechanism that prevents terrestrial organisms from overheating?

11. Property: Water has a high freezing point and lower density as a solid than a liquid. • Water is at its densest at 4º C. From ____________________________________________________ • Subsequently, ice floats. • How is this an advantage for aquatic organisms?

12. Ice floats…

13. Property: Water is the solvent for life • Reactions in cells take place in solution • Solution-____________________________________________________ • Water dissolves more substances than any other solvent

14. Water is the universal solvent!

15. Water is the solvent for life • Because of water’s polarity, all ionic compounds, and polar covalent compounds (such as sugar) will dissolve in water • __________________—a substance that has an affinity (love) for water (sugar) • _________________—a substance that repels water (lipids)

16. Practice Free Response Water is a critical compound for the continuity of life. 70% of the Earth’s surface is covered with water that is home to thousands of species. 70% – 90% of a cell’s (organism’s) mass is water. • A. Discuss the chemical and molecular structure of the water molecule that uniquely enables it to support life on this planet. • B. Describe three different contributions that water makes to life on Earth. Explain how each contribution is related to the chemical structure of water.