1. Water and the Fitness of the Environment (for life)
Chapter 2

2. Why is water important to life?
Most cells are surrounded by water
Cells are 70 to 95% water
Water is only substance that exists in all 3 states (solid, liquid and gas) naturally on earth

3. The Polarity of Water and Hydrogen bonding
Polar molecules: elements in the molecule have different electronegativities (a difference greater than .4) and one atom pulls harder in the tug of war for electrons. Electrons spend more time around the more electronegative atom.
Results in a polar molecule.
One side negative
One side positive
The polarity allows the water molecules to form hydrogen bonds
weak molecular attractions between Hδ+ and a negatively charged atom.
Each H2O can form H bonds with up to 4 neighboring molecules.
03_02WaterStructure_A.swf

4. Moderation in Temperature
Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air.
Water has a high specific heat (amount of heat change for 1 g of substance to change by 1 °C), so it can absorb or release large amounts of heat with small temperature changes. Water prevents large temperature fluctuations in coastal biomes. Due to H bonding!
Atoms and molecules have kinetic energy, the energy of motion, because they are always moving.
Heat is a measure of the total quantity of kinetic energy due to molecular motion in a body of matter.
Temperature measures the intensity of heat in a body of matter due to the average kinetic energy of molecules.

5. 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

6. Vaporizaiton/Evaporation
The amount of heat required for 1 g of a substance to change from liquid to a gas. Very high for water b/c the H bonds must be broken.
As the water turns to gas and evaporates, the heat is taken with it and the solution (person) cools = evaporative cooling!
Sweating (humans) and release of water from plants cools terrestrial organisms.
About 580 cal of heat are required to evaporate 1 g of water at room temperature; this is fairly high (break H bonds)

7. Water expands when it freezes
Hydrogen
bond
Ice
Hydrogen bonds are stable
Liquid water
Hydrogen bonds break and re-form

8. Water is insulated by floating ice
Water is unusual because it is less dense as a solid than as a cold liquid.
All other substances contract as they freeze, but water expands.
At temperatures above 4°C, water behaves like other liquids, expanding as it warms and contracting as it cools.
When water reaches 0°C, water becomes locked into a crystalline lattice, with each water molecule bonded to a maximum of four partners. As the water warms to 0°C, the H bonds are disrupted.
If ice sank, eventually all ponds, lakes, and even the ocean would freeze solid and marine life would die off.
Instead, the surface layer of ice insulates liquid water below, preventing it from freezing and allowing life to exist under the frozen surface

9. The Solvent of Life

10. Effective at dissolving ionic and polar substances EX: salt water
Water is the solvent of life – dissolves other substances to form aqueous solutions
Effective at dissolving ionic and polar substances
EX: salt water
Water – solvent – does the dissolving
NaCl – solute – gets dissolved
Hydrophobic – water fearing
Covalent bonds and non-polar molecules
Hydrophilic – water loving
Ionic bonds or polar molecules

11. Biology and the Mole.
Remember that the amount of a substance in chemical reaction is measured in moles.
One mole is 6.02 x 1023 of any substance.
The mass of the substance off the periodic table in grams is equal to one mole.
We measure concentration with Molarity
M= Moles of solute/Liters of solution
To make a 1 molar (1M) solution of sucrose (C12H22O11), we would slowly add water to 342 g (molar mass) of sucrose until the total volume was 1 liter and all the sugar was dissolved. Sometimes it is necessary to heat a solution to dissolve all of the solute.

12. Acids and Bases & their affect on life
A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other:
The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion (H+)
The molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+
The molecule that lost the proton is now a hydroxide ion (OH–) H H O O H O O H H H H H
2H2O
Hydronium
ion (H3O+)
Hydroxide
ion (OH–)

13. Acid Vs. Base A base reduces the H+ conc. of a solution
Some bases accept H+ ions, others release OH- in solution.
Bases have a pH between and 14.
An acid increases the H+ conc. of a solution
Acids have a pH between 0 and 6.999

14. Buffers and biological systems
Figure 5
This diagram shows the diffusion directions for H+, CO2, and O2 between the blood and the muscle cells during exercise. The resulting concentration changes affect the buffer equilibria, shown in the upper right-hand corner of the diagram (yellow)
Buffers minimize changes in pH by accepting H+ ions when needed or donating H+ ions
Organisms use buffers to maintain homeostasis.
Blood pH is 7.4, carbonic acid helps to maintain this pH

15. Water Cycle Water 75 % of Earth’s surface
97 % saltwater 3 % freshwater that we can use
essential for all living things
#1 – Precipitation – rainfall, snowfall etc..
#2 – Evaporation – water  water vapor
#3 – Transpiration – Evaporation from plants.
#4 Runoff – Precipitation on land to ocean

16. Water’s impact on life: Concept Map
Include explanation under the bubble for how each property of water (each “bubble” in the concept map) affects living organisms
Water