1. 2-2 Properties of Water

2. Importance of Water
Water is the most abundant molecule on earth and in all organisms
Liquid water covers 75% of the earth’s surface
Without water life as we know it could not exist
You would die after about 5 days without water!

3. The Water Molecule + + H H H2O H H O
Two hydrogen atoms, one oxygen atom
H H O
Water is polar: part of the molecule is slightly positive and part is slightly negative.
Hydrogen atoms are slightly positive.
Oxygen atom is slightly negative.
Oxygen + + H H

4. Hydrogen bonding Because water is polar it can stick together
The hydrogen of one molecule is attracted to the oxygen of another.
Cohesion is when water molecules stick together
Adhesion is when water sticks to other surfaces

5. Water is not always pure…
Mixture: a substance composed of two or more elements or compounds that are mixed together (not chemically combined).
Two types of mixtures form with water
Solution: mixture of two or more substances that are evenly distributed
Has two parts
Solute- what is being dissolved
Solvent- substance that the solute is dissolved in
Suspension: mixture of water and nondissolved particles

6. Example of a solution All the ions are evenly dispersed in the water
Cl-
Cl-
Na+
Na+
water
Water
All the ions are evenly
dispersed in the water

7. Acids, Bases and pH H2O  H+ + OH-
Copy down the following notes
Acids, Bases and pH
H2O  H OH-
Water  hydrogen ion + hydroxide ion
We can measure how many hydrogen ions a substance has.
pH Scale: a measurement system that shows the concentration H+ ions.
Scale ranges from 0 – 14
0 – 6.9 = acidic: H+ > OH-
7.0 = neutral (water) H+ = OH-
7.1 – 14 = basic H+ < OH-

9. Buffers Weak acids or bases that regulated pH Keeps the pH the same
Maintains homeostasis
There are buffers in our blood