1. We are surrounded by water; we are made of water
The Science of Water
We are surrounded by water; we are made of water

2. Elements of Life
The names of the elements are abbreviated. Often, the abbreviation makes perfect sense (C for carbon) and sometimes it does not (Na for sodium).
There is an abundance of elements on earth and in living systems (over 100 on the Periodic Table) but only 4 elements make up 96% of living organisms. These elements are hydrogen - H, oxygen - O, nitrogen - N, and carbon - C

3. Water in our World Water is necessary for life
Water in our atmosphere helps to keep the planet warm
Our bodies are composed of and dependent on water 3
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4. The Chemistry of Water Simple molecular structure. 1 oxygen atom
2hydrogen atoms
Covalent bond

5. Forming a Water Molecule
Unequal attraction to bonding electrons
Oxygen is a strong electron grabber (high electronegativity)
Hydrogen’s electron cloud tends to hang out close to oxygen, leaving H’s positively charged nucleus all by itself
Orbital representations of hydrogen and oxygen +  – +  – –
A water molecule 5

6. Electron Density is Uneven
The average electron density around the oxygen atom in a water molecule is about 10 times greater than the density around the hydrogen atoms
Dipole
Properties of behavior
A water molecule, with
electron density represented by the shaded blue areas 6
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7. Hydrogen Bonding Representation
In water, hydrogen bonds form between the partially negatively charged oxygen atom and the partially positively charged hydrogen atom
Water molecules, with the hydrogen bonds represented by the dotted lines 7
Source: bonddiagram.gif

8. Polar Bonding Hydrogen Bonding

9. The Chemistry of Water
Each water molecule can form a maximum of four hydrogen bonds at a time

10. Polar Covalent Bonds: Unevenly matched but willing to share.
These bonds can be thought of as two or more dogs that have different desire for bones.  The bigger dog has more strength to possess a larger portion of the bones.  Sharing still takes place but is an uneven sharing.  In the case of the atoms, the electrons spend more time on the end of the molecule near the atom with the greater electronegativity (desire for the electron) making it seem more negative and the other end of the molecule seem more positive.

11. A Quick Overview
Of some of the science basics
What are some of the properties of water that make it so essential to life on our planet? 11

12. Can You Explain Why this Drop Sticks to the Leaf and Grows Larger?12
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13. Or How this Spider Can Walk on Water?13
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14. High Surface Tension Allows water to form drops
Allows water to form waves
Water drops can “adhere” to surfaces even though gravity is pulling on them 14
Source: Photo 2004 Edward Tsang

15. Adhesion
Adhesive forces are attractive forces that occur between two unlike substances
In a narrow glass tube
Water molecules are more strongly attracted to the tube than they are to each other (cohesion)
The cup shape formed at the top of the water is called a meniscus 15
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16. The Chemistry of Water
Adhesion = tendency of "unlike" molecules to cling together
High surface tension allows long water columns to be drawn from roots to leaves – even in a redwood.

17. Water Climbs Trees! Evapotranspiration
The tiny tubes in the root hairs suck up water from the soil
Inside the plant are more hollow tubes (xylem) for transporting water through the plant
Finally, water exits the plant through the tiny openings in its leaves (stomata) 17
Source: Adapted from

18. High Specific Heat Keeps Beaches Cooler in the Day and Warmer at Night!
Specific heat = The amount of energy required to change 1 gram of a substance 1 oC
Water has high specific heat
Absorbs large amounts of heat energy before it begins to get hot
Releases heat energy slowly
Moderates the Earth's climate and helps living organisms regulate their body temperature 18
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19. Forecast for San Diego and Gallup
1/11/06-1/15/06
Water’s high heat capacity has profound effects on climate and ecology. .

20. High Specific Heat Water is slow to undergo changes in temperature.
Much heat must be added or removed before the temperature of water changes much.
HOMEOSTASIS IS POSSIBLE BECAUSE OF WATER
Biochemical reactions take place only within a narrow range of temperatures.

21. Solid, Liquid, and Gas
Water is the only substance which exists under normal conditions on earth as a solid, a liquid, and a gas 21
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22. Ice is Less Dense than Water I
Density of H2O at different temperatures
Temperature oC
Density
g/cm3
(solid)
0.9150
(liquid)
0.9999 4
1.0000 20
0.9982
100
(gas)
0.0006 22
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23. Ice is Less Dense than Water II
This is a very rare property!
Crystal lattice structure of ice
Ice crystal
Sources: 23

24. Ice Melting
Notice that ice has an open lattice structure that collapses when it melts
Click the image above to view the animation in your web browser, or go to 24

25. Can you imagine if ice did not float?
Questions
Can you imagine if ice did not float?
How do you think that would affect the world? 25

26. Ice is Less Dense than Water
This means that ice forms an insulating blanket over water.

27. Water is a Universal Solvent
Being polar allows water to dissolve nearly any substance with an unequal distribution of charges
Water is the best substance that is universally used for transporting dissolved substances
Water dissolves more substances than any other liquid 27
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28. The Chemistry of Water
The ability of ions and other molecules to dissolve in water is due to polarity. A hydration shell forms as water surrounds an ion.
Solution

29. Put them together and you get
Acids and Bases
An acid produces H+
A base absorbs H+
Put them together and you get
SALTS!!!!

30. Acids and Bases
In biology, keeping H+ levels within a narrow range is critically important.
Water is neutral!!!
pH = 7
pH is a measure of proton concentration.
Low pH = lots of H+s = Acid
High pH = few H+s = Base

31. Acids and Bases
Buffers are substances that minimize changes in pH. They accept H+ from solution when they are in excess and donate H+ when they are depleted.
Carbonic acid (H2CO3) is an important buffer in living systems. It moderates pH change in blood plasma and the ocean.