1. The most important inorganic compound for living organisms!
Properties of Water
The most important inorganic compound for living organisms!

2. Water is POLAR!
Water has an unequal distribution of charges…the O atom has a (-) charge & each H atom has a (+) charge.
Polarity refers to the property of having 2 opposite poles.
HOW DOES THIS RELATE?

3. Hydrogen Bonds
The oppositely charged ends of a water molecule can form weak interactions with each other known as HYDROGEN BONDS!
Opposites Attract!

4. Cohesive An attraction of molecules of the same substance
Water can “stick” to itself….surface tension!
Explains why some insects can “walk on water”

5. Adhesive An attraction between molecules of different substances.
Allows for capillary action….draws water out of roots up into the stems.

6. Water has a high heat capacity…what does that mean?
Water is able to absorb large amounts of heat.
As a result, lakes and oceans stabilize air and land temperatures.

7. Ice floats? Yes, Water is more dense as a liquid than a solid!
Prevents lakes & ponds from freezing solid…life can survive at the bottom
Also allows for mixing of nutrients in water

8. Universal Solvent
Most all of our chemical reactions take place in SOLUTIONS….comprised of a solute (the substance dissolved) and a solvent (the substance in which the solute dissolves)…water is the greatest solvent on Earth!

9. In summation,
Water is essential for life on Earth!

10. pH and the Importance to Life

11. What exactly is pH?
Well, it stands for the potential of hydrogens, but simply put….
It is a measure of the concentration of H+ ions in a solution

12. Water hydrogen hydroxide
Acids Bases
Produces H+ ions in solution and have pH values less than 7
Produces OH- ions in solution and have pH values greater than 7
H2O  H OH-
Water hydrogen hydroxide
*Pure water is NEUTRAL and has a pH of 7.

13. pH Scale: 0 Acid 7 Base 14 NOTE: Every # is a factor of 10X!
Stronger Neutral Stronger
0 Acid Base 14
NOTE: Every # is a factor of 10X!

15. Why do we care in BIOLOGY?
Stomach is acidic (help break down food)
Soil pH is key to plant life (Hydrangeas change color based on pH of soil)
Acid Precipitation (affects both aquatic life and plants)
Enzymes function at certain pH
Most biological processes take place in pH close to NEUTRAL ( ), some slightly basic or acidic, in order to maintain homeostasis

16. What is a buffer?
Mixtures that can react with acids or bases to keep the pH within a certain range
Example – buffers in blood to keep pH about 7.4

18. Let’s Watch!!