The Chemistry of WaterThe Chemistry of Water

““When the well’s dry, When the well’s dry, we know the worth of we know the worth of

water”water”--Benjamin Franklin--Benjamin Franklin

Water’s polarity results Water’s polarity results in hydrogen bondingin hydrogen bonding

•Water is a polar moleculeWater is a polar molecule

The charge of the water The charge of the water molecules results in molecules results in hydrogen bondshydrogen bonds

Properties: Hydrogen Properties: Hydrogen bonding results in…bonding results in…• Cohesion—__________________Cohesion—__________________• Adhesion—Adhesion—

____________________________________________________________________________________________________________________

Both responsible for capillary Both responsible for capillary action.action.

• Surface Surface ____________________________________________________________________________________________________________________

Which properties apply Which properties apply here?here?

Property: Water has a Property: Water has a high specific heathigh specific heat• Specific heat—amount of energy to Specific heat—amount of energy to

cause 1 g of a substance to change cause 1 g of a substance to change its temperature by 1its temperature by 1º C. º C.

• Water’s specific heat is Water’s specific heat is ____________________________________

• The reason water’s specific heat is The reason water’s specific heat is high is because a high is because a ____________________________________________________________________________________________________________________

Water has a high Water has a high specific heatspecific heat

• Areas surrounded by water have Areas surrounded by water have moderate temperatures—the water moderate temperatures—the water absorbs the heat—without raising the absorbs the heat—without raising the temperature of the water.temperature of the water.

• At night the loss of the heat by water At night the loss of the heat by water warms the air.warms the air.

• The result—the water itself and the The result—the water itself and the surrounding land have a constant surrounding land have a constant temperaturetemperature

Property: Water results Property: Water results in evaporative coolingin evaporative cooling• Heat of Heat of

______________________________________________________________________________________________________________________________________________________________________________

• This helps moderate earth’s climateThis helps moderate earth’s climate

• As a liquid evaporates, the surface of As a liquid evaporates, the surface of the liquid that remains behind cools the liquid that remains behind cools down. This is down. This is ________________________________.________________________________.

•Stability of temperature in Stability of temperature in lakes and ponds?lakes and ponds?

•A mechanism that prevents A mechanism that prevents terrestrial organisms from terrestrial organisms from overheating?overheating?

How does evaporative How does evaporative cooling result incooling result in

Property: Water has a high Property: Water has a high freezing point and lower freezing point and lower density as a solid than a density as a solid than a liquid. liquid. •Water is at its densest at 4Water is at its densest at 4º º

C. From C. From ________________________________________________________________________________________________________

•Subsequently, ice floats.Subsequently, ice floats.•How is this an advantage for How is this an advantage for

aquatic organisms?aquatic organisms?

Ice floats…Ice floats…

Property: Water is the Property: Water is the solvent for lifesolvent for life

•Reactions in cells take place Reactions in cells take place in solutionin solution

•Solution-Solution-________________________________________________________________________________________________________

•Water dissolves more Water dissolves more substances than any other substances than any other solventsolvent

Water is the universal Water is the universal solvent!solvent!

Water is the solvent for Water is the solvent for lifelife• Because of water’s polarity, all Because of water’s polarity, all

ionic compounds, and polar ionic compounds, and polar covalent compounds (such as covalent compounds (such as sugar) will dissolve in watersugar) will dissolve in water

• __________________—a substance __________________—a substance that has an affinity (love) for that has an affinity (love) for water (sugar)water (sugar)

• _________________—a substance _________________—a substance that repels water (lipids)that repels water (lipids)

Practice Free ResponsePractice Free ResponseWater is a critical compound for the continuityWater is a critical compound for the continuity

of life. 70% of the Earth’s surface is coveredof life. 70% of the Earth’s surface is covered

with water that is home to thousands ofwith water that is home to thousands of

species. 70% – 90% of a cell’s (organism’s)species. 70% – 90% of a cell’s (organism’s)

mass is water.mass is water.

• A. Discuss the chemical and molecular A. Discuss the chemical and molecular structure of the water molecule that uniquely structure of the water molecule that uniquely enables it to support life on this planet.enables it to support life on this planet.

• B. Describe three different contributions that B. Describe three different contributions that water makes to life on Earth. Explain how water makes to life on Earth. Explain how each contribution is related to the chemical each contribution is related to the chemical structure of water.structure of water.