Water Chemistry

Component of Life Life would not exist without water Only known life to us Life began in water Cells are 70-95% water Earth is 75% covered with water Exists as solid, liquid, and a gas naturlly on Earth

Property #1: Cohesion Hydrogen bonds that hold water molecules together Water breaks bonds easily and reforms easily-water has structure Important: High surface tension = hard to break surface layer of water. Animals can use to stand, walk, run

Cohesion http://biology.uwsp.edu/faculty/esingsaa/Biol350/reference/lecture7/Hbonds.gif

Property #2: Adhesion Clinging of one substance to another Water clings to surface of vessels in plant. Overcomes gravity. Cohesion keeps water molecules together moving upward

#3 High Specific Heat Requires high amount of heat (energy) to be absorbed/lost to change 1 g of water by 1 degree Celsius Can absorb/release high amounts of heat Moderates Earth’s climate-75% of Earth is water Makes Earth habitable

#4 High Heat of Vaporization Large amount of heat(energy) needed to change 1g of liquid water to gas Hottest molecules lost (highest amt of energy), cooler ones left behind Moderates climate. Warm air circulated to cold poles. Evaporative cooling-plants and animals prevent overheating

#5 Solid Water Floats! No other element in solid form floats in same liquid form – Unique to water Water in sold form (ice) is less dense than liquid form (water) Ice floats! Lakes, ponds, oceans still habitable when top freezes – Ice insulates water

#6 Water is Neutral pH value of 6-7.5 Not acidic or basic Changes to the pH can damage or cause death to organisms, Ex. Acid rain Your body has ways to deal with acidic/basic conditions – Buffers – neutralizes