Title: Water’s Unique Properties Allow Life to Exist on Earth. 9-14-2012

Water’s unique properties allow life to exist on Earth. Water is a polar molecule. Polar molecules have slightly charged regions because Oxygen doesn’t share electrons equally with Hydrogen. Electrons have what kind of a charge Label the charge on the water molecule below O H H

Water’s unique properties allow life to exist on Earth. Water is a polar molecule. Polar molecules have slightly charged regions because Oxygen doesn’t share electrons equally with Hydrogen. Electrons have what kind of a charge (negative) Label the charge on the water molecule below O- +H H+ What do opposite charges do?

Water’s unique properties allow life to exist on Earth. Properties of Water Water is a polar molecule High specific heat capacity High heat of vaporization Adhesion Cohesion Three states of matter Kinetic energy differences Repels hydrophobic materials

Waters High Specific Heat Capacity Water makes hydrogen bonds with other water molecules You have to break the hydrogen bonds BEFORE waters temperature will increase In other words, water absorbs a large amount of heat without changing temperature Because of this water is very good at moderating climates of coastal ecosystems Who has more extreme seasons, Chicago or Florida? Water also helps maintain the correct temperatures in cells

Waters High Heat of Vaporization Water molecules absorb energy (heat) as they change state from a liquid to a gas Evaporative Cooling: when an area or body becomes cooler as water evaporates off of it Sweating/ perspiring

Adhesion & Cohesion Cohesion: water molecules are attracted to each other because of their polar charges Responsible for surface tension (demo) A “skin” that forms across the top of water Adhesion: water molecules are attracted to other polar molecules and ions because of their charge distribution Responsible for Capillary Action: Water moves up thin tubes against gravity Plants use this to get water from the roots all the way up

Water exists naturally in 3 states on Earth Solid (ice) Ice is less dense than liquid water Ice floats and insulates bodies of water underneath Liquid Gas (water vapor)

Water is a Great Solvent Water can dissolve other polar molecules Water can dissolve ionic compounds (salt)

How Organisms Exploit Waters Properties Water is a good medium for metabolic processes because of its solvent properties Osmosis Diffusion Water can moderate temperature Ice as an insulator Evaporative cooling Moderation of coastal climates Capillary Action (in plants) Surface tension Transpiration