Introduction to Water.ppt

1、Introduction to Water,Created by Dr. Michael Pidwirny, Department of Geography, Okanagan University College, BC, CA,evaporation,Soil and Water,What is Soil?,The interface between the atmosphere, hydrosphere, biosphere and lithospherenaturally occurring layers of mineral and organic constituents that

2、 differ from the underlying parent material in their physical, chemical, and mineralogical properties,Rock,What is Water?,A binary compound that occurs at room temperature as a clear colorless, odorless, tasteless liquid Freezes into ice below 0 C and boils above 100 C Necessary for life on earth (h

3、uman, animals and plants) Constitutes 60-70 % of the human body,,1050,Oxygen,Hydrogen,Hydrogen,Electro positive,Negative,Polarity,Symmetrical (e.g., CO2),H-O : 0.97 A H-H : 1.54 A,angstroms,H+,H+,O-,= +,-,H2O,Hydrogen bond,Gives structural strength Bond depends on temperature:Bonds are weaker at hig

4、her temperature Positive end attraction with neg. end of other water molecules,http:/ nature of water due to unevenly distributed charges,O=,H+,H+,Polymer type of grouping,Cations: Na+, K+, Ca2+ become hydrated through their attraction to the negative end of water (Oxygen side) Anions or negatively

5、charged clay surfaces attract water through positive hydrogen side,J. L. Fulton, Y. Chen, S. M. Heald, and M. Balasubramanian, Rev. Sci. Instruments., 75(12), 5228-5231 (2004).,http:/www.pnl.gov/cmsd/highlights/images/20050727water.jpg,http:/courses.cm.utexas.edu/jrobertus/ch339k/overheads-1/water-s

6、tructure.jpg,Does water swell and shrink with Temperature?,1,0.998,0.996,0.994,0.992,0.990,-10,0,10,20,30,40,50,Density (g cm-3),Temperature (0C),40C,www-ssrl.slac.stanford.edu/./structure_ice.jpg,http:/www.columbia.edu/cu/biology/courses/c2005/ purves6/figure02-15a.jpg,Representation of Ice Melting

7、,www.cscs.ch/./representations/index.html,periods,groups,Dimitri Mendeleev,Temperature range in liquid phase for H2x compounds,100,50,0,-50,-100,0,50,Molecular Weight,Temperature (0C),100,H2O,H2S,H2Se,H2Te,Boiling point,Freezing point,Hydrogen sulfide,Hydrogen selenide,Hydrogen telluride,(2+16=18),(

8、2+32=34),(80),(130),The sum of the atomic weights of all atoms in a molecule,If water were an ordinary compound whose molecules are subject to weak forces, its boiling and freezing points would fall below hydrogen sulfide,Strong hydrogen bonding between water molecules prevents this so that liquid w

9、ater acts more like a gel, cluster, or polymer,Water occurs in all three states (solid, liquid, and gaseous) at prevailing temperatures on the earths surfaceExample: Ice cubes in a glass at room temperature,Soil Solution,aqueous liquid phase of the soil and its solutes,Hydrogen Bonding,Water is a po

10、werful solvent,How salt dissolves in water, do plants obtain the nutrients in the soil?,http:/www2.mcdaniel.edu/Biology/botf99/nutrition/catex.jpg,www2.mcdaniel.edu/./botf99/nutrition/soils.htm,Clay minerals as sources of ions,http:/www.ca.uky.edu/agc/pubs/agr/agr11/fff00003.gif,Typical ion concentr

11、ations (can be much higher in arid regions due to high evapotranspiration (ET) and concentrating effects),K+ 1-10 (mg/L)Na+ 1-5Ca+2 20-200Mg+2 2-50Si+4 10-50SO4-2 60-300Cl- 50-500,Solutes exist in solution as:,Free hydrated ions Complexes with ligands organic or inorganic(H2O, NH3+, F-, OH-, Cl-, CN- or EDTA, citric acid, DTPA, NTA,),“Free” hydrated ions,http:/ complexes,http:/journals.iucr.org/e/issues/2006/11/00/ng2089/ng2089scheme1.gif,Ligand Exchange Mechanisms ML6 + Y- ML5Y + L- ,www.meta-