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Water

Water. The Most Important Inorganic Molecule. Source: http://en.wikipedia.org/wiki/Image:SnowflakesWilsonBentley.jpg. Properties of Water. Oxygen bonded to two hydrogens (H 2 O) Polar covalent molecule Oxygen has a higher affinity for electrons than hydrogen Oxygen is slightly negative

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Water

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  1. Water The Most Important Inorganic Molecule Source: http://en.wikipedia.org/wiki/Image:SnowflakesWilsonBentley.jpg

  2. Properties of Water • Oxygen bonded to two hydrogens (H2O) • Polar covalent molecule • Oxygen has a higher affinity for electrons than hydrogen • Oxygen is slightly negative • Hydrogen is slightly positive Source: http://en.wikipedia.org/wiki/Image:Water_molecule.svg Source: http://en.wikipedia.org/wiki/Image:Water_molecule_dimensions.svg

  3. Molecules form H-bonds • Hydrogen bonds are weak magnetic forces Source: http://en.wikipedia.org/wiki/Image:3D_model_hydrogen_bonds_in_water.jpg

  4. H-bonds hold molecules in ice at fixed intervals • Ice forms a crystal lattice • Ice is less dense than water • H2O maximum density at 4 ºC WATER Source: http://en.wikipedia.org/wiki/Image:Liquid_water_hydrogen_bond.png ICE Source: http://en.wikipedia.org/wiki/Image:Cryst_struct_ice.png

  5. Properties of Water that are Advantageous to Life • Adhesive • Attracted to molecules of other substances • Can be absorbed into materials or cling to surfaces • Cohesive • Attracted to each other • Results in capillary action and high surface tension Source: http://en.wikipedia.org/wiki/Image:Spider_web_Luc_Viatour.jpg Luc Viatour Source: http://en.wikipedia.org/wiki/File:Capillarity.svg

  6. High specific heat capacity • Takes a lot of energy to change its temperature • Helps organisms resist changes in environmental temperature • Evaporation of sweat cools organisms • Density decreases as it freezes • Ice floats on liquid water • Ice = insulation on water bodies Source: http://en.wikipedia.org/wiki/Image:Iceberg_with_hole_near_sanderson_hope_2007-07-28_2.jpg

  7. Transparent • Light can pass through it • Photosynthesis is possible inside water bodies • A versatile solvent • Dissolves more solutes than any other liquid • Hydrophillic = water soluble • Hydrophobic = water insoluble • Amphipathic = molecules with water soluble regions AND water insoluble regions

  8. Amphipathic Molecules in Water • Detergents and phospholipids are common amphipatic Molecules • Form miscelles, liposomes, bilayers in water (“hide” hydrophobic tails; “expose” hydrophillic heads)

  9. pH of Water • Water can ionise • Pure water naturally has H+ and OH- ions • pH of pure water is 7

  10. Acids in Water • Acids ionise or react to produce H+ • Lowers the pH

  11. Bases • Ionises or reacts to form OH- ions in water • Increases pH

  12. Buffers • Solution of a weak acid with its conjugate base • Reversibly reacts with H+ and OH- so that pH changes are resisted • In mammals the blood pH is tightly controlled by a series of buffers

  13. Did you know? H2O is the only substance on earth to be found naturally in all three states: • Solid • Liquid • Gas Source: http://en.wikipedia.org/wiki/Image:The_Earth_seen_from_Apollo_17.jpg

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