1. The Chemistry of Water

2. The Water Molecule Made of 3 atoms
2 Hydrogen atoms
1 Oxygen atom
These atoms are held together by covalent bonds
Covalent bond = sharing of electrons between the atoms

3. Water is Polar Polarity
= an uneven distribution of electrons between the oxygen and hydrogen atoms.
Oxygen acts as a negative charge
Hydrogen acts as a positive charge
HOWEVER!!! The entire water molecule has a neutral charge.
This is the most important property of water

4. Hydrogen Bonds
Polar water molecules act like magnets and attract each other
Hydrogen Bonds
The attraction of the Hydrogen end (+) of one molecule to the Oxygen end (-) of another water molecule.
One hydrogen bond is weak, BUT many hydrogen bonds are strong

5. Cohesion
The attraction between molecules of the same substance (e.g. water).
Results in surface tension - a measure of the strength of water’s surface
Allows some insects and spiders to walk on water. Or allows paper clips to float!

6. Adhesion Attraction between molecules of different substances
Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.
Responsible for capillary action - water molecules will “tow” each other along when in a thin tube
Plants use to draw water out of soil

7. Homeostasis Ability to maintain a constant internal environment.
Water is important to this process because:
a. Makes a good insulator
b. Resists temperature change
c. Universal solvent
d. Coolant

8. Solutions & Suspensions
Water is usually part of a mixture.
A combination of two or more substances where both maintain their individual characteristics
There are two types of mixtures:
Homogenous
Heterogenous

9. Homogenous Mixtures A solution is a homogenous mixture
A homogenous mixture formed when a substance is dissolved in another (ions are separated)
Evenly distributed
Uniform throughout
A solution is a homogenous mixture
Has two parts
SOLUTE = Substance that is being dissolved
Exp. = salt or sugar
SOLVENT = Substance into which the solute dissolves
Exp. = water

10. Solution

11. Heterogeneous Mixtures
Components remain distinct, so you can tell them individually
Sand & water form a heterogenous mixture called a suspension
Over time the particles settle out

12. Heterogeneous Mixtures
A colloid is a heterogeneous mixture in substances don’t dissolve but separate into tiny pieces.
Water keeps the pieces suspended so they don’t settle out.
Examples: milk & mayonnaise

13. Acids, Bases & pH H2O  H+ + OH-
1 water molecule in 550 million naturally break down into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)
Hydrogen Ion Hydroxide Ion
Acid Base
H2O  H+ + OH-

14. Acids are substances that release hydrogen (H+) ions when dissolved in water
The more H ions released, the stronger the acid
Bases release hydroxide (OH-)ions when dissolved in water

15. The pH Scale Indicates the concentration of H+ ions Ranges from 0 – 14
pH of 7 is neutral (pure water)
pH 0 – 6.99 is acid … high H+, low OH-
pH 7.01 – 14 is basic… high OH-, low H+
Each pH unit represents a factor of 10 change in concentration

16. Acids
Strong Acid =
pH 1-3

17. Bases
Strong Base =
pH 11 – 14

18. Buffers
Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH.
Weak Acid
Weak Base

19. HOMEWORK
Notes Assignment # 8