1. Water and Life
Chapter 3
Unit 1

2. Contributions to Life on Earth
Evoulution of Life
Cells are 70%-95% water
Covers about ¾ of the Earth
solid, liquid, and gas

3. Water’s Polarity
Polar molecule: overall charge is unevenly distributed
(+) of hydrogen attracted to (–) of oxygen
Maximum of 4 bonds with other water molecules
Hydrogen bonds between water molecules
Covalent bonds between O and H2

4. 4 Emergent Properties Cohesive behavior Moderation in Temperature
Floating of Ice on Liquid
Solvent of Life

5. Cohesive Behavior Cohesion Adhesion Surface Tension
Measure of how difficult to stretch or break surface

6. Moderates Temp. on Earth
High specific heat
Amt. of heat absorbed or lost for 1g of a substance to change its temp.
Large bodies of water act as Heat Sinks
Absorb heat from sunlight during day and release heat during night

7. Moderates earth’s climate
Evaporative Cooling
High Heat of Vaporization (Boiling point)
Quantity of heat a liquid must absorb to be converted into gaseous state
Moderates earth’s climate
Tropical air moves pole ward, vapor releases heat as condenses into rain
Keeps organisms from overheating

8. Floating of Ice on Liquid
Less dense as a solid than as a liquid
Prevents deep bodies of water from freezing
As freezes, releases heat to water below
Freeze-> H bonds release heat
Melts-> H bonds break absorbing heat

9. Versatile Solvent Caused by polarity
Solution: homogenous mixture of 2 or more substances
Solvent
Solute
Hydrophilic: affinity for water (polar)
Hydrophobic: does not have affinity for water (nonpolar and nonionic)

10. pH Scale Acids: pH < 7 Bases: pH > 7
Increases relative H+ of a solution
HCL  H+ + Cl-
Bases: pH > 7
Reduces the relative H+ of a solution
NAOH  NA++ OH-

11. Buffers Minimize wide fluctuations in pH
Combinations of H+ donor and H+ acceptors