1. Making Life possible - Water

3. * Water statistics Covers 75% of Earth’s surface
(why understanding it is important!)
Covers 75% of Earth’s surface
97% oceans
3% freshwater
2% (of Total) in ice caps and glaciers
1% in lakes, underground, or in atmosphere (usable by humans)
Makes up 70% of the human body
92% of blood plasma
80% of muscle tissues
60% of red blood cells

4. Physical properties Water:
Is clear, colorless, odorless, and tasteless
* Colors, tastes and odors are caused by substances dissolved in the water.
Boils at 100°C
Freezes at 0°C
Density = 1.0 g/mL (at 4°C)
Water is a Polar Molecule

5. Water
A water molecule (H2O), is made up of three atoms --- one oxygen and two hydrogen. H O 1

6. Water is Polar
In each water molecule, the oxygen atom attracts more than its "fair share" of electrons
The oxygen end “acts” negative
The hydrogen end “acts” positive
Causes the water to be POLAR
However, Water is neutral (equal number of e- and p+) --- Zero Net Charge

7. HYDROGEN BONDS
Extraordinary Properties that are a result of hydrogen bonds.
Cohesive behavior
Resists changes in temperature
High heat of vaporization
Expands when it freezes
Versatile solvent
Hold water molecules together
They form, break, and reform with great frequency

8. Organisms Depend on Cohesion
Hydrogen bonds hold the substance together, a phenomenon called cohesion
Cohesion is responsible for the transport of the water column in plants
Cohesion among water molecules plays a key role in the transport of water against gravity in plants
Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels.

9. Cohesion - click me
The cohesion of water molecules leads to two other important properties:
Surface Tension – the attraction between water molecules at the surface of the liquid
High Specific Heat – it takes a lot of energy to warm up water and it takes a very long time for warm water to cool off

10. Surface Tension click me
Resistance of a liquid to an increase in surface area because H bonds in H2O
Ex: floating a paper clip, “water striders”, water beading on waxed car
Air
Water

11. WATER IN SPACE– SWEET – Click me
JUST WHEN YOU THOUGHT WATER POSSIBLY COULDN”T BE ANY MORE AWEOMER THAN IT ALREADY IS!
WATER IN SPACE– SWEET – Click me

12. Moderates Temperatures on Earth
Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air.
Water can absorb or release relatively large amounts of heat with only a slight change in its own temperature.
Specific Heat is the amount of heat that must be absorbed or lost for one gram of a substance to change its temperature by 1oC.

13. Universal Solvent
Solvent – a substance that dissolves another substance
Your able to dissolve more as temperature goes up.
pop carbonation example
What dissolves in water?
Salt
Sugar
Carbon Dioxide
Oxygen
MANY more!
For an object to dissolve in water it must also be a polar molecule!
This is why oil and water do not mix, oil is NON polar

14. Density of Water Most dense at 4oC Contracts until 4oC
Expands from 4oC to 0oC
The density of water:
Prevents water from freezing from the bottom up.
Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.
Makes transition between season less abrupt.

15. Acids and Bases
An acid is a substance that increases the hydrogen ion concentration in a solution.
Any substance that reduces the hydrogen ion concentration in a solution is a base.
Some bases reduce H+ directly by accepting hydrogen ions.
Strong acids and bases complete dissociate in water.
Weak acids and bases dissociate only partially and reversibly.
There is only 1 molecule out of 554,000,000 water molecules that is dissociated.

16. Viscosity!!! Remember volcanoes
The resistance to flow
High viscosity is sticky; remember examples given in class
Low viscosity is runny the lowest being water.