Water & Solutions Water is a unique molecule necessary for life –Found in all cells –Surrounds all cells

Water & Solutions Water’s unique properties are due to –Polarity – an uneven distribution of shared electrons within the molecule

Water & Solutions Water’s unique properties are due to –Polarity – an uneven distribution of shared electrons within the molecule –Hydrogen Bonds – a weak chemical attraction between polar molecules the attraction between the positively charged hydrogen of water and the negative charge that exists on other polar molecules including water itself due to waters polarity

Water & Solutions Hydrogen bonds create –Cohesion – attraction between molecules of the same substance –Adhesion – attraction between molecules of different substances

Water & Solutions See Figure 5 on textbook page 31 Hydrogen Bonding in Water Is this cohesion or adhesion?

Water & Solutions Hydrogen bonds create –Surface Tension – property of the surface of a liquid to resist an external force the surface can stretch and will not break easily caused by cohesion –Capillary Action – process in which water molecules move up through a narrow tube the attraction of water to the walls of the tube pulls the water up more strongly than gravity pulls it down caused by adhesion

Water & Solutions Surface Tension

Water & Solutions Capillary Action

Water & Solutions Solution –mixture of two or more substances in which the solute molecules are evenly distributed in the solvent solute – substance that is dissolved solvent – substance that does the dissolving –“like dissolves like” water is able to dissolve ionic compounds and other polar compounds, but not nonpolar compounds.

Water & Solutions Why does vegetable oil separate from water when they are mixed in the same container?

Water & Solutions Why does vegetable oil separate from water when they are mixed in the same container? Vegetable oil is nonpolar, and water is polar.

Water & Solutions

Acids, Bases, and pH Pure water will ionize in the following way to create hydrogen, and hydroxide ions. H2OH2OH+H+ +OH - water hydrogen ion hydroxide ion

Water & Solutions pH scale (0-14) –a system to measure the concentration of H + ions in a solution Acids  H + > OH - –pH values < 7 Bases  H + < OH - –pH values > 7 Neutral –pure (distilled) water has a pH = 7

Water & Solutions

pH scale (0-14) –each whole number represents a factor of 10 on the scale –Ex:a solution with a pH of 5 is 10 times as many hydrogen ions as one with a pH of 6 –How much more acidic is a solution with a pH is 2 than one with a pH is 5? 2->3 = 10 times 3->4 = 10 times 4->5 = 10 times 10x10x10 = 1,000 time more acidic!

Water & Solutions

Buffers –Weak acids or bases that prevent sudden changes in pH in living organisms