1. The chemical reactions of all living things take place in an aqueous (water based) environment. Thus, water is one of the most important compounds found in living things!
Properties of Water
Chapter 2
Revised Jul 2014

2. Roughly 70 percent of an adult’s body is made up of water.
By the time a person feels thirsty, his or her body has lost over 1 percent of its total water amount.
Although a person can live without food for more than a month, a person can only live without water for approximately one week.
Your brain is 75-85% water and plays a vital role in your body's response to dehydration. It controls water intake through altering thirst and varying the water excretion from your kidneys.
Water Fun Facts

3. B. Chemical formula = H20 --2 parts hydrogen --1 part oxygen
A. Water is the single most abundant compound in most living things
B. Chemical formula =
H20
--2 parts hydrogen
--1 part oxygen 8P 8N 1P 0N
Bohr Model for water
(covalent bonds)

4. D. Water compound is a POLAR covalent
1. Polar = the electrons
are unevenly shared
between the hydrogen
and oxygen atoms.
2. Oxygen pulls on the e- greater than the H . . .so at any moment, the shared e- are more likely closer to the oxygen

5. Structure of Water: Polarity
Polarity: electrons are not shared equally.
Causes the oxygen to be negatively charged and the hydrogens to be positively charged.
(–)
(+) O H

6. 3. What effect does “polar” have?
--water has a partial pos pole and partial neg. pole
--like a magnet

7. E. Hydrogen Bonding
1. The partial + and partial – charges allow H2O molecules to attract to each other or stick together through Hydrogen Bonds
2. Hydrogen bonds are WEAK bonds that can be easily broken
3. H-bonds = responsible for H20 special properties . . .

8. Hydrogen Bonds Hydrogen Bond:
(–)
(+) O H
Hydrogen Bonds
Hydrogen Bond:
Weak attractive force between a negatively charged hydrogen and a positively charged atom (on a different molecule.)

10. F. PROPERTIES OF WATER:
1. Strong cohesion
and
adhesion forces!

11. Cohesion= attraction between molecules of the SAME substance
Explains why water beads up

12. . . . Due to the hydrogen bonding of surface molecules to each other
Example 2: Cohesion leads to water having a high surface tension
. . . Due to the hydrogen bonding of surface molecules to each other
Images from:

13. b. Adhesion = attraction between molecules of DIFFERENT substances
Explains why microscope slides stuck together

14. capillary action in plants
Example of both cohesion and adhesion of water working together . . .
capillary action in plants

15. TedEd video clip on water

16. 2. Ability to absorb heat: Water can absorb large amounts of
thermal energy
before its own
temperature begins
to rise.
Water acts like a heat buffer for the globe.

17. 3. Ice is less dense than liquid water
Image from:

18. 4. Ability to form solutions
Water is VERY EFFECTIVE in dissolving many other substances
“Universal solvent”

19. Water is the ‘universal solvent’
Solution = liquid consisting of uniform mixture of two or more substances
Two parts of a solution:
Solvent = liquid (dissolving agent)
Solute = substance dissolved
EXAMPLE:
Water = solvent Koolaid powder/sugar = solutes Kool-aid = solution

20. Remember the rule to make a solution: “Like dissolves like.”
Since water is polar, it will dissolve ions and other polar substances (like salt!) Na+ Cl-
Hydrophilic = Water Lover
Water will NOT dissolve nonpolar substances

21. Non polar molecules are hydrophobic
Electrons are shared equally in nonpolar molecules. Oil is an example of a nonpolar molecule. It does not form hydrogen bonds. Like dissolves like, therefore, oil (nonpolar) does not mix with water (polar). Nonpolar molecules are hydrophobic (“afraid of water”) because they do not mix with water.

22. Properties of Water—seen in space

23. Simulation: Overview of water properties
Simulation found at:

24. surface tension=
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules
Electronegativity=The attraction of an atom for the electrons of a covalent bond
Electronegativity is the tendency for an atom to pull electrons toward itself. Two atoms of the same element have equal electronegativities; in a covalent bond they share electrons equally, forming a nonpolar covalent bond.