Water and the Fitness of the Environment CHAPTER 3 Water and the Fitness of the Environment

OUTLINE Water’s Polarity and the Effects A. Polarity results in H bonding B. Organism’s depend on the cohesion of water C. Water moderates earth’s temps. D. Ocean’s and lakes don’t freeze solid E. Water is the solvent of life

Outline, Part II Dissociation of water A. Organism’s sensitive to pH III. Acid precipitation threatens the fitness of the environment

WATER Life evolved in it Cells are 70-95% water 71% of earth are oceans Exists in all 3 states: NY,NJ,CT (Uh, solid, liquid, gas…excuse me)

POLARITY Water is Polar, it has an ASSYMETRICAL molecular shape It’s 4 valence orbitals point to the corners of a tetrahedron e-’s spend WAY more time around the Oxygen H bonding orders water into a higher level of structural organization Each water molecule can form 4 H bonds w/neighboring waters. This causes: Cohesive behavior, Resistance to Temp. changes, High Vaporization point, expansion when it freezes, Versatility as a solvent.

Organisms Depend on Cohesion Transpirational pull (cohesion), and adhesion allow plants to survive SURFACE TENSION: The measure of how difficult it is to stretch or break the surface of a liquid Water has a greater surface tension than most liquids: At the air-water interface, the surface molecules are H bonded to each other and the water below. Why does water “bead” on smooth surfaces?

Water Moderates Temperatures Define: Kinetic Energy: Energy of Motion Heat: The total kinetic energy due to molecular motion in a body of matter Temperature: The measure of heat intensity due to the avg. kinetic energy of molecules in the a body of matter

More Temperature Moderation Vocabulary Define: Calorie: The heat required to raise 1gram of water 1 degree Celsius Kilocalorie: 1000 cal, or heat amt. Necessary to raise 1Kg of water 1 degree C.

Water and It’s High Specific Heat It resists Temp. changes when it absorbs/releases heat Specific Heat: Amt. Of heat necessary to raise 1g of a material 1deg. Celsius. Water: 1Cal/g/deg C H bonds absorb heat to break, release heat when they form Much of absorbed heat disrupts H bonds before the temp rises Because so much of the Earth is water, it’s temp is stabilized

Evaporative Cooling Molecules with enough kinetic energy jump from liquidgas, thus lowering the average kinetic energy of the remaining liquid (temperature!) Heat of Vaporization: How much heat is required for 1 gram to convert to a gas For water: 540 Cal/g, or 2260Joules/g. A Joule is .239 Cal. This cools animals, plants, and the planet

Hey! Ice Floats! So lakes, oceans don’t freeze solid The H bonding between H2O molecules forms rings, so ice is less dense Water is densest at 4 deg C As water freezes, it releases heat into the water below it, thus insulating it further

Water…The solvent of life! Why? It’s POLAR! Define: Solution: Liquid that is a completely homogeneous mixture of 2 substances Solvent: Dissolving agent in a solution Solute: The substance dissolved in a solution. An aqueous soln: water is solvent.

Hydrophilic Substances Hydrophilic: Water loving Ionic Compounds: charged regions of polar water have an electrical attraction to ions. Water surrounds individual ions, separating and shielding them from one another Polar compounds: Charged regions of water molecules have an affinity for the oppositely charged regions of other polar molecules

Hydrophobic Substances Water “fearing/hating” Nonpolar compounds (symmetrically charged) are NOT water soluble

A water soluble protein

Solute Concentrations in Aqueous Solutions Solute concentration and pH are important quantitative properties Molecular Weight: Sum of weight of all atoms in a molecule in Daltons Mole: Amt. of a substance so that it’s mass in grams=its molecular weight in daltons.

Example: Sucrose C12H22O11 : C= 12X12= 144 dal H=1X22= 22 dal O=16X11= 176 dal ________ 342 dal So 342g=1 Mole Molarity : Moles of solute/1 liter of solution: In this case add 342g to 1L water

Water, A salted

Dissociation of water H2O + H2O-- H3O + OH- The H ion transfers from the H bond w/ O to unshared orbitals of O. This equation simplified is: H2O<--- ->H+ + OH- At equilibrium, most of the water is NOT ionized

Organisms are Sensitive to pH Changes ACIDS and BASES: At equilibrium, in pure water at 25* C, H ions=OH ions An ACID increases H+, removes OH- ( OH- combines with H+ to make water). H+>OH-. Weak acids dissociate partially and reversibly. A Base decreases H+, Increases OH- and H+<OH-

pH Scale Measures the degree of acidity [H+][OH-]=1.0X10-14 Most biological fluids are within the range from 6-8 Each pH unit represents a logarithmic (tenfold) difference in H+

The pH of some Aqueous Solutions

Buffers (the vampire slayer?) Substances that minimize large, sudden changes in pH They’re usually a combo of H+ donor and H+ acceptors in a solution of weak acids or bases They donate H+ when depleted, accept H+ when in excess

Acid Precipitation and Environmental Fitness Considered acidic precip.if pH<5.6 In W. Virginia, recorded rainfall @pH 1.5!!!!! SO2 and NO in air react w/ water to form sulferic and nitric acids. Fossil fuels (COAL) and autos are the biggest source Lowers soil pH, leaches heavy metals Aquatic ecosystems are threatened first Cure? Pollution control (scrubbers, reduction of burning)

Hydrogen Bonds in Water

ICE, ICE BABY you tube ICE ICE Baby