Water and Life How the properties of water enable life to exist

Cohesion occurs when water molecules stick to each other Cohesion occurs when water molecules stick to each other. Adhesion is when water molecules stick to other surfaces.

Adhesion allows water to stick to the veins of plants, and Cohesion allows the water to stay together as it travels through the veins.

Surface tension Is this cohesion or adhesion?

Solid water is less dense than liquid water: Ice floats!

Large bodies of water are “Heat Sinks”: Maritime climates vs. Continental climates Climate in San Francisco: Climate in

Water is life’s solvent: it dissolves Salts and Sugars

Water is a polar molecule As a result it can form Hydrogen bonds. This gives water its unique properties.

Polar Covalent bonds: One atom shares its electrons unevenly with another. This forms a Polar Molecule

In Polar Molecules, one end of a polar molecule is slightly negative while the other end is slightly positive.

Polar molecules are like magnets: When they come near each other, they form a weak attraction called a Hydrogen bond. Weak attractions singularly Strong when many are together Help to hold together the 3D shapes of complex molecules (like DNA and enzymes) In liquids, regularly form, break, and reform as molecules move Easily broken by enzymes or a drastic change in conditions (heat, salinity, pH…)

Hydrogen bonds make water molecules sticky Notice how the opposite charges of each water molecule are facing each other--

Hydrogen bonds can form between any two polar molecules.

Because of Hydrogen Bonds, Solid water is less dense than liquid (so it floats!) Ice is less dense than water because the molecules lose the energy to break hydrogen bonds; there is more space between molecules.

Water is the Solvent of Life Solutions form when polar molecules dissolve salts or other polar molecules Solution, solvent, solute, Hydrophilic, Hydrophobic www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

In liquids, water can dissociate to form hydroxide (OH-) and hydrogen (H+) ions.

Summary Water is a polar molecule because the oxygen end is slightly negative and the hydrogen end is slightly positive Polar Molecules can form hydrogen bonds Hydrogen bonds make water molecules sticky—causing cohesion and adhesion These qualities allow life to exist

1.The properties of water are extremely important to trees!! Identify and explain each property of water a tree relies on.

2.Like dissolves like: So, polar molecules will dissolve in other polar molecules. Explain why nonpolar molecules, like lipids will not dissolve in water.