WATER

Why is Water Important? Can dissolve just about anything (including gold)! Liquid water can carry substances around cells, organisms, ecosystems, or the planet Allows chemical reactions to occur Helps to shape enzymes – special proteins needed for life’s chemical reactions

How Unique is Water?? Water is one of only 3 naturally occurring inorganic liquids (mercury and ammonia) Only chemical compound that exists in all 3 states—solid, liquid, and gas Extremely large liquid range (0oC - 100oC) Expands, becomes less dense as a solid

Water is a polar compound… Shares e- unevenly http://web.visionlearning.com/custom/chemistry/animations/CHE1.7-an-H2Obond.shtml Oxygen atom in water takes on a slight negative charge, the Hydrogen atoms take on a slight positive charge

Water’s polarity allow it to form Hydrogen bonds Weak bonds that form between positively charged H and negative end of another polar compound http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html

In liquid water, H bonds form and break quickly http://www.visionlearning.com/library/module_viewer.php?c3=1&mid=57&l= In solid ice, H bonds lock water molecules in place (making it less dense)

Water has ability to absorb large amounts of energy Freezes at 0oC Boils at 100oC

Hydrogen bonding accounts for Cohesion Adhesion

Water is the universal solvent: Ionic Compounds http://programs.northlandcollege.edu/biology/Biology1111/animations/dissolve.html Other polar compounds

Mixtures Homogeneous- even throughout Heterogeneous- uneven throughout

Solutions Mixtures in which one or more substances are uniformly distributed in another Solute – substance being dissolved (ex. salt or sugar) Solvent – substance in which the solute dissolves (ex. water) Amount of solute dissolved = concentration

Other Mixtures Suspension – particles do not dissolve “hang” or suspend in water due to movement of water molecules Over time they settle out Colloid – particles do not settle out over time

Size of Particles Solution (small) Colloid (intermediate) Suspension (large)

pH scale

pH scale H2O will spontaneously split to form H+ and OH- H+ and OH- will further react to form H3O+ (hydronium) and OH- (hydroxide) In pure water, H3O+ = OH- , so water is neutral pH scale is based on the number of H3O+ and OH- in solution

Acids and Bases An acid has more H3O+ while a base has more OH- Ex. neutral acid

pH scale Ranges from 0 - 14 7 is neutral (water) pH < 7 = acid pH > 7 = base Based on a factor of 10

pH in an organism Most cells work best around pH 7 Too high or too low pH cause enzymes in the body to stop working To prevent large pH swings, organisms use buffers