Chemistry of Life WATER

Team Time Get out your Is it Alive Paper from last class. 1)As a team list 3 things that are living and 3 things that are non-living based on the evidence collected last class. 2) List as many reasons you can think of for the importance of water. What properties make it important?

Water Investigations You have received a template for 5 investigations into the properties of water which make it so useful and important to life. In the allotted time your objective is to correctly complete the observations at each station and record your results. Return to your teams when finished.

1. MC.1.B.3 Investigate the properties and importance of water and its significance for life: Polarity, pH, Cohesion, Adhesion, Surface tension, Capillary Action

Water H2O Most abundant liquid on earth Universal solvent 2 hydrogen and 1 oxygen Most abundant liquid on earth In almost everything Universal solvent Dissolves solutes

Polarity In each water molecule, the oxygen atom attracts more than its "fair share" of electrons (uneven distribution of charge) The oxygen end “acts” negative The hydrogen end “acts” positive Causes the water to be POLAR However, Water is neutral (equal number of e- and p+)

pH As water mixes in solutions, it can break into 2 parts: hydroxide (OH-) and hydrogen (H+) ions pH is the measure of how basic (OH-) or acidic (H+) a substance is

pH: Acids Contain more hydrogen (H+) pH from 0-6

pH: Neutral Has an equal number of hydrogen and hydroxide ions.

pH: Bases Contain more hydroxide ions (OH-) pH from 8-14

Strong vs. Weak Strong means it is further on the ends. Strong can be very dangerous Weak means it is in the middle, near neutral Weak is usually not dangerous

Cohesion Because of hydrogen bonding, its molecules stick to each other. Water sticks to itself

Surface Tension Cohesion results in Surface tension (a measure of the strength of water’s surface) Produces a surface film on water allows insects to walk on the surface of water

Adhesion Water sticks to other substances. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.

Capillary Action Capillary action-water molecules will “tow” each other along a surface. Caused by cohesion and adhesion Example: water moving up plants against gravity and paper towels soaking up water.