1. CHPT. 3:
The Chemistry of Water
Prof. Dr. Samih Tamimi

2. The Water Planet

3. The polarity of water molecules results in HYDROGEN BONDING -
(weak inter-molecular bond)
Remember, H2O is a polar covalent bond + +

4. The polarity of water molecules results in HYDROGEN BONDING -
each molecule can bond to max. of 4 neighbor molecules via. hydrogen bond    

5. The polarity of water molecules results in HYDROGEN BONDING -
(inter-molecular bond)
weak bond
-constantly reforming

6. Properties of Water that contribute to its importants for life:
1)Cohesion
*water sticks to water

7. Properties of Water that contribute to its importants for life:
1)Cohesion

9. Properties of Water that contribute to its importants for life:
2)Adhesion - (adhesive)
*Water sticks to other surfaces

10. Properties of Water that contribute to its importants for life:
2)Adhesion -
*Water attracted to other surfaces

11. Water transport in trees uses Cohesion and Adhesion

12. Water is difficult to stretch or break the surface.
Properties of Water that contribute to its importants for life:
3) High Surface Tension-
*Cohesion of water molecules to eachother at the surface of the body of water.
Water is difficult to stretch or break the surface.

13. Properties of Water that contribute to its importants for life:
4) High Specific Heat =
- amount of heat energy needed to raise 1 g. of a substance 10C

14. Properties of Water that contribute to its importants for life:
4) High Specific Heat =
It takes “a lot” of heat for water to increase 1oC
b/c of the hydrogen bonds!!!
- water is able to absorb heat, without increasing in temperature, better than many substances

15. Compared with most other substances, water absorb FAR MORE HEAT before it raises 1oC in temp.

16. *) Water stabilizes temperatures. = acts as a heat sink
As a result:
*) Water stabilizes temperatures. = acts as a heat sink
H20 absorbs and stores MUCH heat from sun & air
and it only slightly changes temp. of H2O

17. and it only slightly changes temp. of H2O
Water stabilizes temp. =
For water to increase in temp. water molecules must be made to move faster… this requires breaking hydrogen bonds, and THAT absorbs heat.
and it only slightly changes temp. of H2O

18. therefore:
Water will change temperature less when it absorbs or looses an amount of heat… than other substances
Water’s moderating effect on the climate under water

19. Water is also able to retain heat better than many substances (resists cooling)
For water to decrease in temp. water molecules must be made to move more slowly. This requires forming hydrogen bonds. The forming of H-bonds gives off heat (hence counteracting cooling tendencies as heat is lost from liquid water)

20. heat - measure of total K.Energy of molecule due to molecular motion
Remeber
heat - measure of total K.Energy of molecule due to molecular motion
temp. - measures average speed of the molecule

21. Water is also able to retain heat better than many substances (resists cooling)
As a result, the air around the cooling water becomes warm
(remember.. The forming of H-bonds gives off heat!)

22. Amount of energy needed to change a substance to a gas.
Properties of Water that contribute to its importants for life:
*) Heat of vaporization = high
Amount of energy needed to change a substance to a gas.
-Water resists evaporating (vaporizing) b/c H-bonds must be broken in order for water to transition from liquid to the gas state.

23. - Bodies of H2O do not freeze from bottom up
Properties of Water that contribute to its importants for life:
5) Less dense as a solid than liquid
- Bodies of H2O do not freeze from bottom up

24. Solids and Liquids
Water
Benzene
Floats
Sinks

25. Stable H-bonds
unstable H-bonds

26. Ability of Water to dissolve some substances and not others
Properties of Water that contribute to its importants for life:
6) Water is versatile Solvent
Ability of Water to dissolve some substances and not others
H2O dissolves substances to which it can readily H-bond - - attracted to b/c the substance has a full or partial charge.

27. Properties of Water that contribute to its importants for life:
6) Water is versatile Solvent
Hydrophilic - ionic & polar compnds -loves water ex. salt

30. Properties of Water that contribute to its importants for life:
6) Water is versatile Solvent
Hydrophobic - nonpolar compnds
-repels water ex.
cell membrane/lipids

32. Changing pH in a water system can indicate pollution…

33. Acid precipitation
normal precipitation

34. Acid Rain

35. Acidification of oceans
dissociates
Supposed to be used for the animals