chemical and physical features of seawater and the world ocean if there is magic on this planet, it...

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Chemical & Physical Properties  Physical property – properties that describe a substance without changing the identity of the substance. Physical change – change that does not result in the production of a new substance, only the appearance of the substance Physical change – change that does not result in the production of a new substance, only the appearance of the substance  Chemical property – properties that describe how a substance changes into a completely different substance Chemical change – change that results in the production of another substance Chemical change – change that results in the production of another substance

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Chemical and Physical Features of Seawater and the World Ocean If there is magic on this planet, it is contained in water. Loren Eiseley Well, me dont swim too tough so me dont go in the water too deep. Bob Marley What is Water ? Introduction the stuff covers 70% of the Earth Brainstorming activity Chemical & Physical Properties of Water Categorization activity Defend your categories If time permits why the answer to life is 104.5 Chemical & Physical Properties Physical property properties that describe a substance without changing the identity of the substance. Physical change change that does not result in the production of a new substance, only the appearance of the substance Physical change change that does not result in the production of a new substance, only the appearance of the substance Chemical property properties that describe how a substance changes into a completely different substance Chemical change change that results in the production of another substance Chemical change change that results in the production of another substance Common Properties of Water Physical Properties Chemical Properties Cohesion/Surface tension Found in all three states on the earth Universal Solvent dissolves more substances than any other common liquid Conduction of heat highest of all liquids (except for mercury) pH water dissociates into anions (OH - ) and cations (H + ) Latent heat of vaporization highest of all common substances Polarity water has positive and negative ends Latent heat of fusion high for a molecule of its size (melting/freezing) Hydrophobic effect Heat capacity highest of all common solids & liquids Density max at 4C for pure water Viscosity relatively low for a liquid References Castellano, A. (2006) Victoria Beach Castro, P. & M.E. Huber (2005) Marine Biology, 5 th ed. McGraw-Hill Higher Education, Boston, MA. Chemical Properties of Water PlanetWater.au.com Retrieved on Feb 3, 2007 from floating water 5 (2006) wester Lower, S. (2007) H 2 O a gentle introduction to the structure of water. Retrieved on Feb 3, 2007 from Nybakken, J.W. & M.D. Bertness (2005) Marine Biology, An Ecological Approach, 6 th ed. Pearson Education, Inc., San Francisco. Perlman, H. (2006) Water properties Water Science for Schools. USGS. Retrieved on Feb 3, 2007 from Petrucci, R.H. (1982) General Chemistry Principles and Modern Applications, Macmillan Publishing Co. Inc., New York. The Water Molecule Two hydrogen atoms, one oxygen atom H atoms form 105 angle This angle produces an asymmetrical dipole. Slight (+) charge on the H atoms and slight (-) charge on the O atoms. O HH 105 The Water Molecule These slight charges cause the (+) H atoms of one water molecule to attract the (-) O atoms of other water molecules. These weak bonds are called hydrogen bonds. Water can hydrogen bond with other substances aside from itself. O H H O HH O HH Why does ice float? Density-Temperature Relationship Background Temperature is a measure of kinetic energy (K E ). As K E decreases, hydrogen bonds stay formed and break less. Water molecules stay closer together until Explanation As the temperature approaches 4C, less dense ice clusters begin to form in the liquid. At 0C when all water molecules become locked in the rigid ice lattice, the hydrogen bonds actually hold molecules farther apart than at 4C. This creates spaces making the water less dense. Why does ice float? Density-Temperature Relationship Graph The cohesion or mutual attraction of water molecules creates a flexible barrier on the surface of water. This helps support aquatic insects such as water striders (Halobates sp.) How can water bugs stride across water without breaking the surface? How can water bugs stride across water without breaking the surface? Surface tension and cohesion Why do fish not get electrocuted when lightning strikes the ocean? Conductivity Explanation Conductivity is a property that measures the ability of a substance to transmit heat, electricity, or sound. Pure water is not a good conductor of electricity. Its conductivity is about 20 dS/m. (Compare with silver the highest conductivity with 63 x 10 6 S/m) In addition, the electrical charge of lightning usually spreads instantaneously along the surface of the water from the location of the strike and to a lesser degree below the surface at the strike site. Fish in other areas are not affected. Background Heat energy of molecular motion Water can absorb or give up heat by conduction (molecular exchange of heat) or convection (mixing) Explanation Water can hold heat longer and release heat more slowly than land. Temperature differential between land and ocean will cause uneven heating of air masses which drive winds and moderate any drastic temperature changes. Why do coastal areas have slower temperature changes than inland areas? Why do coastal areas have slower temperature changes than inland areas? Heat capacity Off-shore breeze On-shore breeze Fats and oils are nonpolar molecules. These compounds do not have slight regions of charge like water does. These compounds do not have slight regions of charge like water does. Therefore water molecules are not attracted to nonpolar molecules and actually can be repelled by them. Basis for cell membranes and the water repellency of marine mammals and birds. Basis for cell membranes and the water repellency of marine mammals and birds. Why dont fats and oils dissolve in water? Why dont fats and oils dissolve in water? Polarity Because water is polar, it dissolves most substances, especially other polar molecules and compounds composed of ions, atoms or molecules that carry an electrical charge. These ionic compounds are often called salts. NaCl (salt) most common dissolved salt in ocean. There are many others. Seawater is a solution of these salts. Why does water dissolve more substances than any other common liquid? Why does water dissolve more substances than any other common liquid? The Universal Solvent Salt crystal Seawater Sources of salts and dissolved solids: Erosion of rocks and soil Breakdown of organisms Condensation of rain from the atmosphere Releases from hydrothermal vents Seawater is 96.5% water 3.5% dissolved compounds Salinity Measured in parts per thousand (ppt) Grams of salt left behind when 1000g of water evaporate Grams of salt left behind when 1000g of water evaporate Average value 35 ppt or 35 Range from 0 near river mouths to 40% in the dead sea. Globally, seawater salinity remains constant. Rule of constant proportions states that the percentage of various ions in seawater remains constant. Total amount of dissolved salts in seawater. Surface Salinities of the Oceans Dissolved compounds in seawater Inorganic substances (salts, nutrients) Dissolved gases Organic compounds (fats, oils, vitamins, amino acids, proteins) Nitrates and phosphates (usually in excess as pollution) Pollution (DDT, PCBs, chlorinated hydrocarbons that are synthetic) Dissolved Gases Primarily nitrogen, carbon dioxide, oxygen N 2 biologically inert. CO 2 needed for photosynthesis and pH buffering. O 2 required for respiration.stories/s htm Factors that Affect Salinity Salinity increases due to freezing of seawater. freezing of seawater. evaporation. evaporation. Salinity decreases due to melting of icebergs and sea ice. melting of icebergs and sea ice. precipitation. precipitation. run-off from rivers. run-off from rivers. pH The amount of hydrogen ions in a substance is referred to as pH. pH = (pondus hydrogeni or power of hydrogen pH = (pondus hydrogeni or power of hydrogen pH = -log 10 [H+] pH = -log 10 [H+] Scales ranges from 0 to 14. Scales ranges from 0 to 14. Therefore, a pH of 14 means that the water is very alkaline (basic) while pH 1 means it is acidic. A pH of 7 is neutral. Seawater pH The carbonic acid bicarbonate carbonate system keeps seawater at a pH value between 7.5 and 8.4. The oceans are an enormous sink for atmosphere CO 2 The Carbon Buffering System Seawater has an unusually large capacity to absorb CO 2. CO 2 + H 2 O H 2 CO 3 (carbonic acid) H 2 CO 3 H + + HCO 3 (bicarbonate ion) H 2 CO 3 H + + HCO 3 (bicarbonate ion) HCO 3 H + + CO 3 2- (carbonate ion) HCO 3 H + + CO 3 2- (carbonate ion) Work Cited Kreger, Chris. "Acid Mine Drainage: Alkalinity." Exploring the Environment: Water Quality Wheeling Jesuit University. 2 Oct Lower, Stephen. "A gentle introduction to water and its structure." H2O Oct "October 2006 Archives." [Weblog The Marine Electronics Weblog] Oct Panbo. 1 Oct Water Conductivity Lenntech Water Treatment & Purification B.V.. 1 Oct Woodruff, Steve W.. "Water & Weather." Los Angeles Pierce College Weather Station. 1 Oct 2008. The Salinity-Temperature-Depth Relationship in the World Oceans Part One Depth Profiles Seawater General Trends Temperature and salinity determine the density of seawater. Colder water is more dense; therefore, it sinks. Colder water is more dense; therefore, it sinks. Saltier water is more dense; therefore, it sinks. Saltier water is more dense; therefore, it sinks. Which is more variable on the earth? Temperature or salinity? Which would have a greater effect on the density of seawater? Temperature or salinity? Global Sea Surface Temperature This image shows the temperature of the ocean water at the surface. Measurements were taken from August 6-11, The temperature scale is in Celsius. Cold temperatures are shown in pink to purple, moderate temperatures in aqua to green and warm temperatures in yellow to red. This particular data set was taken by the NOAA-16 satellite. NOAA-16 is part of the TIROS series of polar-orbiting, environmental satellites. Image courtesy of The National Oceanic and Atmospheric Administration (NOAA) The National Oceanic and Atmospheric Administration (NOAA)The National Oceanic and Atmospheric Administration (NOAA) Surface Salinities of the Oceans Biogeographic

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