1. Properties of Water

2. Polarity of Water No net charge
Oxygen end is a bit negative; hydrogen end is a bit positive
This polarity attracts other polar molecules; and repels nonpolar molecules

3. More about Polarity
Polar molecules attracted to water are called hydrophilic or water loving.
Nonpolar molecules repelled by water are called hydrophobic or water dreading.

4. Hydrophilic or Hydrophobic
Water and salad oil and other lipids?
Water and sugar?

5. Hydrogen Bonds
When a hydrogen atom bonded to one molecule is attracted to the slightly negative area (often N or O) of another molecule.
Very weak individual bond.
Can be a “strong” force if there are many H bonds.

7. Temperature Stabilizing
Compared to other liquids, water can absorb more heat energy before its temperature increases measurably.
Much incoming energy breaks hydrogen bonds, but does not increase motion of molecules

8. San Bernardino Burbank Santa Barbara 73° 100° 90° Riverside 96°
Fig. 3-5
San Bernardino
100°
Burbank
90°
Santa Barbara 73°
Riverside 96°
Los Angeles
(Airport) 75°
Santa Ana
84°
Palm Springs
106°
70s (°F)
80s
Pacific Ocean
90s
100s
Figure 3.5 The effect of a large body of water on climate
San Diego 72°
40 miles

9. Cohesion Water sticks to water
Hydrogen bonds pull water molecules on the surface inward, resulting in high surface tension. This is cohesion.
Allows water bugs to stay on top

10. Adhesion Water sticks to other molecules
Water molecules will climb up a tube because the molecules stick to the sides of the tube. Then cohesion among water molecules encourages movement.

11. Water as a Solvent Ions and polar molecules readily dissolve in water.
It is the largest component of your blood, which contains many solutes
Solute: substance that is dissolved

12. Why these properties?
Hydrogen Bonding

13. Water is neutral Acids: pH <7 etc. Bases: pH >7 etc.
Water dissociates into OH- and H+
Water is neutral because there are equal numbers of OH- and H+
Acids: pH <7 etc.
Bases: pH >7 etc.
Each pH unit is a 10X change in H+

14. The Water Cycle

15. Where is the Water? 72%
Most cells are 70-95% water