Making Life possible - Water

* 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

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

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

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

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

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.

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

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 http://wine1.sb.fsu.edu/chm1045/notes/Forces/Liquids/Forces03.htm

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

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.  

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

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.

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.

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