2.2 Properties of Water

LEQ: How does water behave as a solvent?• Reading 32.1, 2.3

• Activator: connecting concepts– When sugars are broken down to produce usable

carbon and energy for cells, a large amount of heat is released. Explain how the water inside a cell helps to keep the cell’s temperature constant.

• Key terms – solution, pH

2.2 Properties of Water

Compounds with a partial or full electric charge can dissolve in water.• Solutions:

– Solvents dissolve other substances.– Solutes dissolve in a solvent.

solution

2.2 Properties of Water

• Solvent rules: “Like dissolves like.”– Polar solvents dissolve polar solutes– Hydrophilic: “water-loving”

2.2 Properties of Water

• Nonpolar solvents dissolve nonpolar solutes:– Polar and nonpolar separate– hydrophobic – “water-fearing”

2.2 Properties of WaterWater’s unique properties allow it move and store heat in solution.• Movement provides thermal energy

– Charges create an electric field (think static).– Water molecules ionize!

2.2 Properties of Water

Hydrogen bonds are organized into networks.• Proton-hopping:

– Moves proton through network

– Sensitive to acids, bases

2.2 Properties of Water

• Pure water is a neutral solution: – Water associating and dissociating is proportional– pH of 7.0 (the occasional “hop”)– Low reactivity pure water pH 7

2.2 Properties of WaterSome compounds release or accept protons in solution.• pH measures conc. of H+ in sol’n inversely

– acids donate H+ in water.– Increases proton-hopping (reactivity)– pH drops as H+ increases

more acidic

stomach acid pH between 1 and 3

2.2 Properties of Water

• A base removes hydrogen ions from a solution.– Accepts hopping protons, removes others– H+ drops– pH greater than 7

bile pH between 8 and 9

more basic

2.2 Properties of Water

Summary:• The most important thing:

– What was the important thing that you learned about water today?

- 2nd….- 3rd…..

• Explain the concept of proton-hopping. How does this relate to the concept of pH?