2. The Water Molecule: Covalent Bonding

3. 2.2 The Properties of Water

4. The Water Molecule The Chemical formula for Water is H2O
Overall, Water is Neutral, because it has same amount of protons (+) as it does electrons (-).
The breakdown:
Oxygen has: 8 (+) and 8 (-)
2x Hydrogen has: 2 (+) and 2 (-)
Total: 10 (+) (-)
NEUTRAL!

5. ...HOWEVER, There’s more to H2O With 8 protons, water’s Oxygen atom has a stronger pull on the electrons in the molecule than the single protons found in each Hydrogen atom.

6. THE RESULT: electrons spend more time around the oxygen atom than the 2 hydrogen atoms.
Therefore, water has a partial negative charge at one end, and a partial positive charge on the other.
Due to this “uneven sharing” of electrons, the water molecule is said to be POLAR.
Water molecules are partially negative
by the Oxygen atom.
Water molecules are partially positive
by the 2 Hydrogen atoms.

7. Because of their partial positive and negative charges, polar molecules such as water can attract each other.
The attraction between a hydrogen atom with a partial positive charge and another atom with a partial negative charge is known as a Hydrogen Bond.

8. Hydrogen Bonds

9. Hydrogen Bonds

10. Water is a Universal Solvent
Because water is a polar molecule, it is able to form multiple hydrogen bonds, which account for these special water properties:
Cohesion and Adhesion
Less Dense as a Solid
High Heat Capacity
Water is a Universal Solvent

11. Cohesion vs. Adhesion

12. Cohesion – an attraction between molecules of the same substance.
Water on Wax paper

13. Adhesion – an attraction between molecules of different substances
Adhesion – an attraction between molecules of different substances. Water on a Glass surface

14. Another Picture…

15. Water is less dense as a Solid

16. Water is less dense as a Solid
What does this mean?
ICE FLOATS!

18. Water has a High Heat Capacity Or simply,
Water can hold onto lots of Heat Energy
This is important for a few reasons...
1. Oceans temps stay relatively stable for aquatic life.
2. A Cell’s activity generates lots of heat, heat that is readily absorbed and managed by WATER.

19. 1. Solutions 2. Suspensions
Rarely does Water exist in its pure form
It is typically part of a Mixture.
There are 2 main types of mixtures:
1. Solutions
2. Suspensions

20. Water is known as a Universal Solvent
Solutions – type of mixture in which all components are evenly distributed.
There are 2 parts to any solution
1. Solvent – substance that does the dissolving.
2. Solute – substance that is dissolved in a solution
Water is known as a Universal Solvent

22. Salt Dissolved in Water

23. A solute dissolves in the solvent.
Solutions continued
Example – When Table Salt (the solute), is placed in water (the solvent), the water dissolves it.
A solute dissolves in the solvent.

24. Suspension

26. Water keeps things suspended.
2. Suspensions – type of mixture in which the particles are nondissolved and stay suspended in the liquid or gas.
Water keeps things suspended.

27. Acids, Bases and pH H2O  H+ + OH-
One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)
Hydrogen Ion Hydroxide Ion
Acid Base
H2O  H+ + OH-

30. Acids, Bases, and pH
The separation of water molecules into ions causes solutions to be acidic, basic, or neutral.
H2O  H+ and OH-
The pH scale measures how acidic or basic a solution is.
pH of 7—Neutral: Equal concentrations of H+ and OH-
pH below 7—Acidic: Relatively high concentration of H+
pH above 7—Basic: Relatively high concentration of OH-

31. The pH Scale Indicates the concentration of H+ ions Ranges from 0 – 14
pH of 7 is neutral
pH 0 up to 7 is acid … H+
pH above 7 – 14 is basic… OH-
Each pH unit represents a factor of 10X change in concentration
pH 3 is 10 x 10 x 10 (1000) stronger than a pH of 6

32. Acids
Strong Acids have a pH of 1-3
Produce lots of H+ ions

33. Bases Strong Bases have a pH of 11 to 14
Contain lots of OH- ions ewer H+ ions

34. Buffers
Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization).
Produced naturally by the body to maintain homeostasis
Weak Acid
Weak Base