Should we control a
chemical that:
Causes
excessive sweating
and vomiting.
Is a major component in acid
rain.
Can cause severe burns in its
gaseous state.
Accidental
inhalation can kill
you.
Contributes to erosion.
Decreases the effectiveness
of car brakes.
Has been found in tumors of
terminal cancer patients.
What is the chemical?
Dihydrogen
Otherwise
monoxide
known as H2O
Chapter 3
Water and the Fitness of
the Environment
Question?
What molecule Is the most
common In living Cells?
Water - most cells are 70 - 95%
water.
The Water Planet
Properties Of Water
Be
ready and able to discuss
several of the following
properties.
Focus on definitions and
examples.
Review water structure and
H-bonds from Chapter 2.
Liquid Water Is
Cohesive
Water
sticks to water.
Why?
Because the polarity of water
results in hydrogen bonding.
Liquid Water is
Adhesive
Water
sticks to other
molecules.
Why?
Hydrogen bonding.
Water transport in trees uses
Cohesion and Adhesion
Water Has A High
Surface Tension
The
surface of water is
difficult to stretch or break.
Why? Hydrogen bonding.
Water Has A High
Specific Heat
Specific
Heat - the amount of
heat needed to raise 1 g of
the substance 1 degree C.
Why?
Hydrogen bonding.
Heat
Total
quantity of kinetic
energy due to molecular
motion.
Temperature
Measures
the average speed
of the molecules.
Celsius Scale
Will
be used for most of our
temperature measurements.
O oC - water freezes
100 oC - water boils
37 oC - human body
Water Stabilizes
Temperature
Water
can absorb and store a
huge amount of heat from the
sun.
Result - climate moderation
Result - organisms are able
to survive temperature
changes.
Fig. 3-5
Los Angeles
(Airport) 75°
70s (°F)
80s
San Bernardino
100°
Riverside 96°
Santa Ana
Palm Springs
84°
106°
Burbank
90°
Santa Barbara 73°
Pacific Ocean
90s
100s
San Diego 72°
40 miles
Water Has A High Heat
Of Vaporization
Heat
of Vaporization:
the quantity of heat a liquid
must absorb for 1g of it to
convert to a gaseous state.
Evaporative Cooling
Result:
Water
cools organisms from
excessive heat buildup.
Why?
Hydrogen bonding
Water Expands When
It Freezes
The
distance between water
molecules INCREASES from
the liquid to the solid form.
Why?
Hydrogen bonding
Solids and Liquids
Water
Benzene
Floats
Sinks
States of Matter
Solid
Liquid
Gas
Result
Aquatic
life can live under ice.
Water Is A Versatile
Solvent
Water
will form a solution
with many materials.
Why?
Hydrogen bonding
Solution
Homogeneous
mixture of two
or more substances.
Solvent
The
dissolving agent.
The material in the greater
quantity.
Solute
The
substance that is
dissolved.
The material in the lesser
quantity.
Hydrophilic Materials
Materials
that dissolve in
water.
Hydro - water
philic - to like or love
Have ionic or polar regions
(polar covalent bonds) on their
molecules for H+ bonds.
Hydrophobic
Materials
that repel water.
Hydro - water
phobic - to fear
Have non-polar covalent
bonds. Ex - lipids.
Solution Concentration
Usually
based on Molarity.
Molarity - the number of
moles of solute per liter of
solution.
Moles
The
molecular weight of a
substance in grams.
One Avogadro’s number of
molecules.
6.02 X 1023
One Mole of each
Sugar
Copper Sulfate
Sulfur
Mercury Oxide
Sodium Chloride
Copper
Comment
AP
Biology students should
be able to calculate solutions
in Molarity.
Dissociation of Water
Water
can sometimes split into
two ions.
In
pure water the concentration
of each ion is 10-7 M
Adding
certain solutes
disrupts the balance between
the two ions.
The two ions are very
reactive and can drastically
affect a cell.
Acids
that can release H+
Example: HCl
HCl
H+ + ClMaterials
Acid Rain
Acid Rain
Bases
that can absorb H+
Often reduce H+ by producing
OHExample: NaOH
NaOH
Na+ + OHMaterials
Neutrals
Materials
that are neither
acids nor bases.
Candice - IA
Homework
Read
chapter 3, 4
Lab - Macromolecules
Chapter 3 – Wed. 8/27
Chapter 4 – Fri. 8/29
pH Scale
A
logarithmic scale for
showing H+ concentration
pH = - log [H+]
pH Scale
Example:
For a neutral solution:
[H+] is 10-7
or - log 10-7
or - (-7)
or 7
Acids:
pH <7 etc.
Bases: pH >7 etc.
Each
in H+
pH unit is a 10x change
Comment
[H+]
+ [OH-] = 14
Therefore, if you know the
concentration of one ion, you
can easily calculate the other.
Fig. 3-9
pH Scale
0
1
Gastric juice,
2 lemon juice
H+
H+
Battery acid
+
– H
H+ OH
+
OH– H H+
H+ H+
3 Vinegar, beer,
wine, cola
4 Tomato juice
Acidic
solution
5
Black coffee
Rainwater
6 Urine
OH–
H+
OH–
H+
OH–
OH– OH– +
H+ H+ H
Neutral
solution
Neutral
[H+] = [OH–]
Saliva
7 Pure water
Human blood, tears
8 Seawater
9
10
OH–
Milk of magnesia
OH–
OH– H+ OH–
–
OH– OH
OH–
+
H
Basic
solution
11
Household ammonia
12
Household
13 bleach
Oven cleaner
14
Buffers
Materials
that have both acid
and base properties.
Resist pH shifts.
Cells and other biological
solutions often contain
buffers to prevent damage.
Summary
Be
able to discuss the
properties of water.
Be able to measure solution
concentrations in Molarity.
Be able to work pH scale
questions.