Chapter 3 Notes
Water and the Fitness
of the Environment
Concept 3.1
Water is a polar molecule, opposite ends
have opposite charges. A slightly
positive hydrogen is attracted to a
slightly negative oxygen of a nearby
molecule.
The two molecules are held together by a
hydrogen bond
Concept 3.1
–
Hydrogen
bond
+
H
+
–
O
–
+
H
+
–
Concept 3.2
Water will stick to each other with hydrogen
bonds (1/20th as strong as covalent
bonds).
Results of Hydrogen bonds
1) Cohesion: when a substance (water) is
held together by hydrogen bonds
2) Adhesion: the clinging of one substance
to another
Concept 3.2
Adhesion
Water-conducting
cells
Direction
of water
movement
Cohesion
150 µm
Concept 3.2
3) Surface tension: measure of how
difficult it is to stretch or break the
surface of a liquid.
- arrangement of hydrogen bonds
between water molecules on surface
and below
Concept 3.2
Concept 3.2
4) Water stabilizes temperatures because
of its high specific heat.
Specific heat: amt. of heat that must be
absorbed or lost for 1g of a substance
to change its temp. by 1oC.
- ex. hot pot of warm water
Concept 3.2
Santa Barbara 73°
Los Angeles
(Airport) 75°
70s (°F)
80s
San Bernardino
100°
Riverside 96°
Santa Ana
Palm Springs
84°
106°
Burbank
90°
Pacific Ocean
90s
100s
San Diego 72°
40 miles
Concept 3.2
Kinetic energy: energy of motion.
Atoms have kinetic energy because they
are always moving.
Heat: measure of the total quantity of
kinetic energy due to molecular motion.
Temperature: intensity of heat due to
the average kinetic energy of the
molecules
Concept 3.2
Celsius scale( oC): water freezes at 0oC
and boils at 100oC.
Calorie (cal): the amount of heat energy
it takes to raise the temp. of 1g of
water by 1oC.
Kilocalorie (kcal): 1 “food” calorie
Joule (J): another unit of energy. 1 J =
0.239 cal; 1 cal = 4.184 J
Concept 3.2
Molecules of a liquid will stay together
because of attraction. If they move fast
enough they will overcome the
attraction and can enter the air as gas.
Heat of vaporization: quantity of heat
a liquid must absorb for 1g of it to be
converted to gas
Concept 3.2
5) Water is the solvent of life.
Solution: homogeneous mixture of two
or more substances
Solvent (dissolving agent) + solute
(substance that is dissolved) = solution
Aqueous solution: water is the solvent
Concept 3.2
+ –
+
–
–
+
–+ – +
–
Na+
Na+
Cl–
–
–
+
–
+
–
–+
Cl–
Concept 3.2
Hydration shell: sphere of water molecules
around each dissolved ion
Hydrophilic (hydro=water, philios=love):
any substance that has an affinity to water.
ionic or polar molecules
Hydrophobic (phobos=fearing): any
substance that repels water. Nonpolar or
non-ionic
Concept 3.2
(b) Lysozyme molecule (purple) in an aqueous
environment
(c) Ionic and polar regions
on the protein’s surface
attract water molecules.
Concept 3.2
Mole (mol): molecular weight of a
substance
Molarity: number of moles of solute per
liter of solution
Concept 3.3
A hydrogen atom shared by two water
molecules in a hydrogen bond can shift
from one molecule to another.
Hydrogen ion (H+), charge is +1
Hydroxide ion (OH-), charge is -1
The proton binds to another water
molecule making H3O+.
Concept 3.3
H
H
O
H
H
O
H
2H2O
O H
H
Hydronium
ion (H3O+)
O
H
Hydroxide
ion (OH–)
Concept 3.3
Acid: substance that increases the [H+]
of a sln.
- ex. HCl -> H+ + ClBase: substance that reduces the [H+] of
a sln. Also, increase the [OH-].
- ex. NH3 + H+ -> NH4+
NaOH -> Na+ + OH-
Concept 3.3
The pH of a sln. is the negative logarithm
of the [H+]
- pH = -log[H+]
- neutral sln. [H+] is 10-7
-log 10-7 = -(-7)= 7
- If acid is added and [H+] is 10-5, the
[OH-] is 10-9.
Concept 3.3
Concept 3.3
0 More
1 acidic
2
3 Acid
4 rain
5 Normal
6 rain
7
8
9
10
11
12
13 More
14 basic
Concept 3.3
Buffers: substances that minimize
changes in the concentration of H+ and
OH- in a sln.
- buffers accept H+ from a sln. when
they are in excess and donate H+ when
they have been depleted.
- use of carbonic acid in blood