Water Molecules and their Characteristics Water and Seawater Water Molecules and their Characteristics

Atomic Structure The chemical properties of water are essential for sustaining all life forms.Composing 65% of humans and 95% of plants Oxygen- 8 protons,8 neutrons, 8 electrons Hydrogen- 1 proton, 1 neutron, 1 electron Water Molecule H2O- one oxygen atom covalently bonded to two hydrogen atoms at an angle of 105 degrees Strong bonds form due to sharing of electrons The Bent geometry gives a negative charge to the oxygen side and a positive charge to the hydrogen side of the molecule Water is a dipolar molecule like a magnet Water molecules orient relative to one another, each +hydrogen attracts a – Oxygen, forms a weak H bond

Properties of Water Due to H Bonds Cohesion- water molecules stick to one another, causes it to bead up on waxed surfaces Surface Tension- Highest of any liquid, Water can pile up above a containers rim, Water bugs can stand on it Adhesion- water clings to surfaces, will climb up the sides of a glass test tube Capillary Action- very thin tubes will allow water to climb up tube, Plants use capillary action to raise water to tops of trees Water sticks to other polar molecules, NaCl + sodium sticks to - oxygen and –chloride sticks to + hydrogen Universal Solvent- Water is able to dissolve nearly everything, given time it can dissolve more substances in greater quantity than any known substance Water melts and boils at very high temperatures due to H bonds H bonds are very plastic, a water molecule changes partners 10 billion to 100 billion times a second

Thermal Properties of Water Water exists as a solid, Liquid and a gas at earths temperatures Has the capacity to store and release great amounts of heat because the H bonds must be broken Heat is measured in calories(heat required to raise 1 gram of water 1 degree centigrade) Latent Heat of melting- to go from solid to liquid just enough H bonds are broken to allow water molecules to slide past one another. (80 calories) Latent heat of Vaporization- to go from liquid to gas all H bonds must be broken to allow water molecules to move freely, (540 calories) water molecules vaporize into air at 1000 mph Latent heat of Evaporation- to evaporate from the ocean surface at less than 100 degrees C water molecules take heat energy away from surrounding water. Molecules left behind have less heat which explains the cooling effect of evaporation ( requires 585 calories to evaporate, more H bonds must be overcome) Latent heat of Condensation releases heat back into air, cooks food as a steamer and releases enough energy to power thunderstorms and Hurricanes. Latent Heat of Freezing is identical to that of melting( 80 calories)

Global Thermostatic Effects The Sun radiates energy to earth where some is stored in the oceans Evaporation removes this heat energy and carries it high into Atmosphere Cooler upper atmosphere causes condensation into clouds and precipitation This cycle of evaporation and condensation carries huge amounts of heat energy from lower warm latitudes to Higher colder latitudes The heat exchange is efficient The thermal properties of water prevent wide variations in Earths temperature, moderating Earths climate

Water Density Density = mass per unit volume, How tightly the molecules of a substance are packed Thermal contraction- density of most substances increases as temp decreases Water density decreases down to 4 degrees C and then increases from 4 to 0 degrees C as ice begins to form Ice is less dense than water and floats, highly unusual for substances Water at 4 degrees C has a specific gravity of 1.000 g/cm Ice crystals are bulky six sided structures, volume increases by 6%

Seawater Salinity Enough salt is dissolved in the ocean to cover the entire earth in 500 feet of salt Seawater also contains chlorine, sodium, sulfur, magnesium, calcium, and potassium and 80 other chemical elements Salinity of the ocean is 3.5%, usually expressed as parts per thousand 35 , or 35 grams of salt to every 1000 grams of water Salinity variations in open ocean 33 to 38 ppt, the Baltic sea averages 10 ppt Brackish water- where fresh water rivers and rain mix with salt water Hypersaline- Red Sea averages 42 ppt , areas with high evaporation rates like inland Lakes, Great Salt Lake Utah 280 ppt, Dead Sea 330ppt Seasonal Variations in salinity, Miami Beach 34.8 ppt in October to 36.4 in May, Columbia River Oregon .3 ppt in April to 2.6 ppt in May Tap water salinity below 0.8 ppt Processes that Effect Salinity include Precipitation, river runoff, melting and freezing sea ice, Icebergs, evaporation

Hydrologic Cycle Recycle water among the ocean, atmosphere and continents Ocean 97.2% Glaciers, Ice Caps 2.1% Ground Water, Soil .62% Rivers and Lakes .02% Water Vapor in Atmosphere .001%

Seawater Density Halocline- rapid changes in salinity between 300 and 1000 meters, Higher salinity means higher Density Thermocline – rapid changes in temp between 300 and 100 meters, warm surface water with layer of cold Denser water underneath Pycnocline- Layer of rapidly changing density due to Halo and Thermo, acts as a strong barrier to mixing surface and deep water The factors that affect seawater density occur at the surface of the ocean, salinity and temperature changes, the surface density can vary but the deep ocean changes very little Water is not compressible so deep ocean pressures have little effect on the density

Exotic Properties of Cell Water Vicinal Water Exotic Properties of Cell Water

Modified Water Water molecules within a cell that are touching a cell membrane or layers close to it are modified by solvation forces Water in a living cell has solutes like NaCl, potassium, magnesium, phosphate as well as fats, proteins and carbohydrates dissolved in it which change the structure of water A cell has hundreds of surfaces, about 840 acres of cell membrane in a single cell so more than 90% of the water is Vicinal Vicinal water is 3% less dense, Absorbs 25% more heat, and has greater Viscosity than nonvicinal water The properties of water change gradually with increasing temperature, the properties of Vicinal water change Abruptly at specific temperatures 59, 86, 113, and 140 degrees F There is an increase of 20-30% in the ratio of potassium to Sodium at these 4 temperatures. Healthy chemical functioning of the cell depends on this ratio being maintained The mammalian body temperature of 98.6 degrees F falls exactly in between 86 and 113, as far from the two as possible. If 122 was the normal temp between 113 and 140 too many calories would be needed to maintain the temp If 72 had been chosen between 56 and 89 overheating at earths average temp of would have been certain

Acidity and Alkalinity of Seawater Acid – compound that releases Hydrogen ions H+ Alkaline or Base- compound that releases hydroxide ions OH- H2O H+ + OH- PH scale (potential of Hydrogen) measure of acidity or alkalinity of a solution Carbonate Buffering System of the ocean- CO2 combines with H2O to form carbonic acid (H2CO3) Carbonic acid can lose an H to form Bicarbonate HCO3 the Bicarbonate can also lose its H to form a Carbonate ion which will combine with Ca to form Calcium Carbonate which is deposited on the ocean floor Buffering- Calcium Carbonate can come out of solution and the carbonate will pick the H back up to remove it from the water If pH of ocean rises it causes H2CO3 to release H and drop pH If pH of ocean drops HCO3 combines with H to remove it raising pH pH of ocean surface averages 8.1 Seawater can hold almost a thousand times more CO2 than oxygen however it is quickly used up by photosynthesis so there is usually about 60 times more CO2 than oxygen CO2 levels have increased only half of what was predicted from human activities, Have the oceans absorbed the rest?

pH Scale

Carbonate Buffering System of Ocean