We are surrounded by water; we are made of water The Science of Water We are surrounded by water; we are made of water

Elements of Life The names of the elements are abbreviated. Often, the abbreviation makes perfect sense (C for carbon) and sometimes it does not (Na for sodium). There is an abundance of elements on earth and in living systems (over 100 on the Periodic Table) but only 4 elements make up 96% of living organisms. These elements are hydrogen - H, oxygen - O, nitrogen - N, and carbon - C

Water in our World Water is necessary for life Water in our atmosphere helps to keep the planet warm Our bodies are composed of and dependent on water 3 Source: http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-earth.html

The Chemistry of Water Simple molecular structure. 1 oxygen atom 2hydrogen atoms Covalent bond

Forming a Water Molecule Unequal attraction to bonding electrons Oxygen is a strong electron grabber (high electronegativity) Hydrogen’s electron cloud tends to hang out close to oxygen, leaving H’s positively charged nucleus all by itself Orbital representations of hydrogen and oxygen +  – +  – – A water molecule 5

Electron Density is Uneven The average electron density around the oxygen atom in a water molecule is about 10 times greater than the density around the hydrogen atoms Dipole Properties of behavior A water molecule, with electron density represented by the shaded blue areas 6 Source: http://www.llnl.gov/str/October05/Mundy.html

Hydrogen Bonding Representation In water, hydrogen bonds form between the partially negatively charged oxygen atom and the partially positively charged hydrogen atom Water molecules, with the hydrogen bonds represented by the dotted lines 7 Source: www.personal.psu.edu/.../ bonddiagram.gif

Polar Bonding Hydrogen Bonding

The Chemistry of Water Each water molecule can form a maximum of four hydrogen bonds at a time

Polar Covalent Bonds: Unevenly matched but willing to share. These bonds can be thought of as two or more dogs that have different desire for bones.  The bigger dog has more strength to possess a larger portion of the bones.  Sharing still takes place but is an uneven sharing.  In the case of the atoms, the electrons spend more time on the end of the molecule near the atom with the greater electronegativity (desire for the electron) making it seem more negative and the other end of the molecule seem more positive.

A Quick Overview Of some of the science basics What are some of the properties of water that make it so essential to life on our planet? 11

Can You Explain Why this Drop Sticks to the Leaf and Grows Larger? 12 Source: http://www.azeemazeez.com/photos/wallpaper/water800.jpg

Or How this Spider Can Walk on Water? 13 Source: http://static.flickr.com/82/237875014_4d579d57c5.jpg

High Surface Tension Allows water to form drops Allows water to form waves Water drops can “adhere” to surfaces even though gravity is pulling on them 14 Source: Photo 2004 Edward Tsang

Adhesion Adhesive forces are attractive forces that occur between two unlike substances In a narrow glass tube Water molecules are more strongly attracted to the tube than they are to each other (cohesion) The cup shape formed at the top of the water is called a meniscus 15 Source: http://www.wtamu.edu/~crobinson/SoilWater/meniscus2.jpg

The Chemistry of Water Adhesion = tendency of "unlike" molecules to cling together High surface tension allows long water columns to be drawn from roots to leaves – even in a redwood.

Water Climbs Trees! Evapotranspiration The tiny tubes in the root hairs suck up water from the soil Inside the plant are more hollow tubes (xylem) for transporting water through the plant Finally, water exits the plant through the tiny openings in its leaves (stomata) 17 Source: Adapted from http://www.ualr.edu/botany/transpiration2.gif

High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night! Specific heat = The amount of energy required to change 1 gram of a substance 1 oC Water has high specific heat Absorbs large amounts of heat energy before it begins to get hot Releases heat energy slowly Moderates the Earth's climate and helps living organisms regulate their body temperature 18 Source: http://www.exodus.co.uk/pictures/d03hp120c.jpg

Forecast for San Diego and Gallup 1/11/06-1/15/06 Water’s high heat capacity has profound effects on climate and ecology. .

High Specific Heat Water is slow to undergo changes in temperature. Much heat must be added or removed before the temperature of water changes much. HOMEOSTASIS IS POSSIBLE BECAUSE OF WATER Biochemical reactions take place only within a narrow range of temperatures.

Solid, Liquid, and Gas Water is the only substance which exists under normal conditions on earth as a solid, a liquid, and a gas 21 Source: http://www.eskimo.com/~captain/slidesho/Lake_Twenty_Two_Partly_Frozen_Over_and_Snow_Covered.jpg

Ice is Less Dense than Water I Density of H2O at different temperatures Temperature oC Density g/cm3 (solid) 0.9150 (liquid) 0.9999 4 1.0000 20 0.9982 100 (gas) 0.0006 22 Source: http://www.wildthingsphotography.com

Ice is Less Dense than Water II This is a very rare property! Crystal lattice structure of ice Ice crystal Sources: http://www.learner.org/jnorth/images/graphics/t/ice_crystal_Greg_Rob.jpg http://www.solarnavigator.net/images/ice_crystal_lattice.gif 23

Ice Melting Notice that ice has an open lattice structure that collapses when it melts Click the image above to view the animation in your web browser, or go to http://nanosense.org/download/finefilters/MeltingIce.mov 24

Can you imagine if ice did not float? Questions Can you imagine if ice did not float? How do you think that would affect the world? 25

Ice is Less Dense than Water This means that ice forms an insulating blanket over water.

Water is a Universal Solvent Being polar allows water to dissolve nearly any substance with an unequal distribution of charges Water is the best substance that is universally used for transporting dissolved substances Water dissolves more substances than any other liquid 27 Source: http://www.chemistryland.com/CHM107Lab/Lab7/Slime/PourStirPoly2.jpg

The Chemistry of Water The ability of ions and other molecules to dissolve in water is due to polarity. A hydration shell forms as water surrounds an ion. Solution

Put them together and you get Acids and Bases An acid produces H+ A base absorbs H+ Put them together and you get SALTS!!!!

Acids and Bases In biology, keeping H+ levels within a narrow range is critically important. Water is neutral!!! pH = 7 pH is a measure of proton concentration. Low pH = lots of H+s = Acid High pH = few H+s = Base

Acids and Bases Buffers are substances that minimize changes in pH. They accept H+ from solution when they are in excess and donate H+ when they are depleted. Carbonic acid (H2CO3) is an important buffer in living systems. It moderates pH change in blood plasma and the ocean.