Chapter 3 – Water and the fitness of the environment
NEW AIM: What is so important about water?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Why does water have this
bent (v) shape?
Lone pair electrons
VSEPR Theory
O
H
H
Water has a bent geometry because the lone pair electrons in the valence shell of oxygen
repel the electrons in ths O-H bonds giving it a “v” shape.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Electronegativity: An elements attraction (affinity for) electrons.
Remember that affinity for electrons depends on the charge of the nucleus AND the
distance the electrons are from the nucleus. The further they are, the weaker the EM
force. The fewer the protons in the nucleus, the weaker the EM force.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Electronegativity: An elements attraction (affinity for) electrons.
Therefore, as you move left to right on the periodic table, the electronegativity
increases since the nucleus is getting larger, but the distance from the nucleus is
staying the same.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Electronegativity: An elements attraction (affinity for) electrons.
As you move up a group, the electronegativity increases. This is because the valence
shell electrons get closer to the nucleus (they have fewer shells/orbitals) even though
the nuclei have fewer protons.
Fluorine has the highest electronegativity.
Why not neon or helium?
Neon/Helium have a full valence shell and
therefore are already stable all by
themselves and will not attract electrons
to be stable.
In biology, we will focus on elements with
high electronegativity like oxygen and
nitrogen.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
O
H
H
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Oxygen has a higher electronegativity
than hydrogen and therefore the shared
electrons will be more likely to be around
oxygen than hydrogen giving oxygen a
partial negative charge and hydrogen a
partial positive charge.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Polar
vs
Non-polar
covalent bonds
A polar covalent bond results when two elements of different electronegativity form a covalent bond resulting in an
unequal sharing of electrons. One becomes partially negative and the other becomes partially positive. Ex. O-H : the O is
partially neg. and the H is partially positive since oxygen has a higher electronegativity compare to hydrogen.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Polar
vs
Non-polar
covalent bonds
They are called “polar” because they have opposite ends (one end is partial neg. and the other is partial pos.). The Earth
has poles or is polar – north pole and south pole. Bipolar personality disorder – sometimes manic and sometimes
depressed. Magnets are polar – north pole and south pole.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Polar
vs
Non-polar
covalent bonds
A non-polar covalent bond results when two elements of similar electronegativity form a covalent bond resulting in an
equal sharing of electrons. Both ends of the bond are neutral. Ex. C-C or C-H bonds.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
δ = () = partially
δ- = (-) = partially negative
δ+ = (+) = partially positive
Non-Polar Covalent Bonds
Polar Covalent Bonds (δ- on
left, δ+ on right)
Any covalent bond between
two of the same elements:
O-O
C-C
H-H
Etc…
O-H
N-H
S-H
O-C
O=C
Etc…
C-H
Why is the C-H covalent bond considered non-polar while the O-H and
N-H bonds are polar?
Carbon has 6 protons, while hydrogen has 1 proton. Therefore, in terms of nuclei, Carbon wins, but
hydrogen only has one shell and carbon has two. Therefore, the electrons are much closer to
hydrogen than to carbon. The closer distance balances the smaller number of protons in the nucleus
resulting in carbon and hydrogen having a similar electronegativity.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Which bonds are Polar and which are
non-polar?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Polar
and
Non-polar
Molecules
Most molecules are a mix of polar and
non-polar covalent bonds. The ratio will
determine how polar/non-polar the
molecules will be.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
How would multiple water molecules interact with each other?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The partially negative oxygens will be attracted to the partially
positive hydrogens forming what is called a hydrogen bond.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What is the maximum number of H-bonds can a single water
molecule make?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Hydrogen
bonding
A hydrogen bond (H-bond) is a weak
bond (weaker than an ionic or
covalent bond) formed between two
partially charged atoms, one of which
is a hydrogen.
Each water can make up to four H-bonds, one to each
hydrogen and one to each of the lone pairs. In liquid
water, the H-bonds are constantly being formed and
broken.
http://www.visionlearning.com/library/module_viewer.php?mid=57
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
How would multiple water molecules interact with a non-polar molecule?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Water molecules will not bond with
non-polar molecules because nonpolar molecules have no charge to
“stick” to. Water molecules interact
with other charged substances.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The molecule on the right is mostly non-polar (almost all
C-C and C-H bonds). This region is known as the
hydrophobic (water-fearing) end since it will not
interact with water. The other end has some polar
covalent bonds (C=O, O-H, C-O) making the tip of this
molecule hydrophilic (water-loving) because water can
H-bond to this part.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Hydration Cage
This is what water does to a nonpolar molecule…it forms a cage
around it using H-bonds.
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
1. Why is the electronegative trend on the periodic table up and to the
right?
2. Explain why C-H is a nonpolar covalent bond if carbon clearly has a
more positively charged nucleus.
3. Water can form a total of _______________ H-bonds
4. Compare the structure of solid to liquid water and indicate why solid
water is less dense.
5. Define Equilibrium. How is it different from homeostasis?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Compare and contrast
covalent, ionic and hydrogen bonds
Covalent bonds share electrons between two atoms to satisify the valence shells (C-C).
Ionic bonds result from donating elecrons from one atom to another resulting in a full and opposite
charge in each atom, which causes them to attract each other (Na+ Cl-).
Hydrogen bonds occur between partially charged atoms, one of which is typically a hydrogen. They
result because of unequal sharing of electrons in covalent bonds due to differences in electronegativity.
Bond Strengths:
H-bonds are weaker than ionic and covalent bonds since only partial charges hold the two substances
together.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What about Van der Waals Interactions (London dispersion)?
Even non-polar molecules may have some positively and negatively charged region briefly and therefore can
very weakly bind to each other…
Dipole = two poles, or a positive
side and a negative side. For
example, a carbonyl (C=O) is a
dipole as the carbon is partially
positive and the oxygen partially
negative.
Figure 1. Two non-polar molecules (say H2) come into close proximity
Figure 2. By chance, the position of the electrons around one of the molecules (the one of the left) are more on one side of the
molecule than the other causing one side to be ever so slightly negative and the other side to be ever so slightly positive.
Figure 3. This will then induce a dipole in the neighboring molecule as the neighboring molecule’s electrons will be attracted to the
slightly positive region of the first molecule resulting again in an ever so slightly negative side and an ever so slightly positive side. Of
course, the negative and positive will form a very weak interaction.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Weak interactions add up…
Think about velcro.
Velcro consists of on side having numerous tiny hooks
and the other having “fuzz” for each hook to wrap
around. A single hook/fuzz interaction is extremely
weak…
However, hundreds of thousands of such interactions are
additive and become important in the case of velcro
jumping.
Where do we see such additive affects of weak bonds in biological systems?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Weak interactions add up…
Strength in numbers!
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Weak interactions add up…
Where do we see such additive affects of weak bonds in biological systems?
Plasma membrane are stabilized by the additive affect of Van der
Waals interactions between non-polar fatty acid tails of
phospholipids.
The two strands of a DNA molecule are held together
tightly by the additive affect of many, many weak
Hydrogen Bonds
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Weak interactions add up…
Where do we see such additive affects of weak bonds in biological systems?
Geckos have been shown to walk up walls using countless numbers
of Van der Waals interactions…
How Geckos Stick on der Waals
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
How is a water molecule
held together
A water molecule itself is held together by covalent bonds.
?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
How are water molecules
held together
Water molecules are held to each other in liquid and solid (ice)
by hydrogen bonds.
?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What determines the properties of
water?
Structure
(Geometry/Shape and Polarity/charge)
All of water’s properties are the product of its molecular structure/charge. All matter, including yourself, cannot be
properly understood unless you understand the underlying molecular structures.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Water is the only substance in nature to exist in the three common states of matter – liquid, solid, gas
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
This image demonstrates the cohesive (sticks to itself by H-bonds) properties of water. This is
what holds it in droplet form. The leaf us covered with non-polar molecules, which is why the
water will not stick to it (there is no charge to interact with)
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Cohesion gives water surface tension as the water molecules H-bond to each other on the
surface forming a very delicate sheet that insects like this water strider can actually walk on
without breaking.
Chapters
Plant
Nutrition
Transport
Water
and theand
fitness
the environment
Chapter 23 32:
-– The
Chemical
Basis
of ofLife
AIM: What is so important about water?
How do plants get water/minerals from the roots to the leaves against
the force of gravity without a mechanical pump like out heart?
Transpiration
- loss of water from leaves (stomata)
pull xylem sap (water/minerals) upward
- Two properties of water that make this
possible:
a. cohesion (water hydrogen-bonding to
other waters): makes the xylem sap like a
continuous string of “water beads”
b. Adhesion (water hydrogen-bonding to
other molecules): sticks to cellulose walls
of xylem cells
Recall that the xylem is a network of dead cells involved in transporting
water and minerals up from the soil.
Fig. 32.3
Chapters
Plant
Nutrition
Transport
Water
and theand
fitness
the environment
Chapter 23 32:
-– The
Chemical
Basis
of ofLife
AIM: What is so important about water?
How do plants get water/minerals from the roots to the leaves against
the force of gravity without a mechanical pump like out heart?
Transpiration
- water molecule at end of chain in leaf
is heated by solar energy
- This molecule is “knocked” out of the
stomate and evaporates
- As it does this, it pulls on the
neighboring waters that it hydrogen
bonds to (cohesion), the neighbors pull
on their neighbors and so on all the way
to the roots
(Without the suns KE, the water in the leaf would
remain stuck to its neighbors - no pulling force, no
transpiration)
Fig. 32.3
Chapters
Plant
Nutrition
Transport
Water
and theand
fitness
the environment
Chapter 23 32:
-– The
Chemical
Basis
of ofLife
AIM: What is so important about water?
How do plants get water/minerals from the roots to the leaves against
the force of gravity without a mechanical pump like out heart?
Transpiration
- What about adhesion?
- adhesion counters downward pull of
gravity by “grabbing” (hydrogen bonding
to) walls of xylem
- holds water in xylem when
transpiration is not occurring (at night)
Fig. 32.3
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Temperature Regulation
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Heat vs Temperature
For example, the temperature of a small cup of
water might be the same as the temperature of a
large tub of water, but the tub of water has more
heat because it has more water and thus more
total thermal energy.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Heat vs Temperature
Heat is referring to molecular motion. The “hotter” something is, the quicker the molecules are
moving/vibrating. If something hot touches you like a hot iron, the rapidly vibrating molecules
with crash into your skin causing your skin molecules to vibrate rapidly resulting in damage to
the structure of your molecules/cells. It is the measure of the total amount of KE due to
molecular motion in a body of matter.
Temperature is the average motion of all the molecules in a substance. For example, in a glass
of water that is 98.6 F (body temperature) the molecules have a certain average speed (about
700 meters per second). However, some will be moving faster than that and some will be
moving slower. The temperature just tells us the average motion or KE of all the molecules.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What is specific heat?
The amount of “energy” (collisions) it takes
to heat up 1 gram of the substance by 1
degree Celcius. It takes a lot of energy to do
this to water: 1 calorie (cal) of energy to be
exact).
Therefore the specific heat of water =
1 cal/g °C
Another way to say this is specific heat is a
measure of how well as substance resists a
change in temperature.
1 cal = 4.184 Joules (J)
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What is specific heat?
Explain how a stove heats up a pot of
water on the molecular level and then
state why water has such a high
specific heat.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What is specific heat?
Explain why water has a higher
specific heat than ethanol (.59
cal/g/C) on the molecular level.
ethanol
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What is specific heat?
If I put a liter of water and a liter of
ethanol on a stove and heat them
up…what will I observe in terms of
temperature change over time?
ethanol
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Water, because of it H-bonding (cohesive
nature) has a very high specific heat
relative to other molecules. This is because
when molecules collide with the water
molecules, it is difficult to get them
vibrating since those waters are all
sticking to each other. The H-bonds need
to be broken. Think about the analogy in
class where it is easy to push a single
student and get them moving fast, but if
you all hold hands, it becomes more
difficult as I would need to break those
bonds.
Conclusion: water can absorb a great deal of energy without its temperature rising too greatly and vice
versa, which is why it takes quite a bit of time to boil water on your stove relative to boiling another liquid
like ethanol whose specific heat is 0.6 cal/g/°C.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
QUESTION:
If you have 50g of water and you apply
400 calories of energy, by how many
degrees C will the water be raised
assuming 100% energy transfer?
8 degrees C
-50 cal will heat up the 50g by 1C
-You have 8 x 50 cal and therefore you
will raise it 8 degrees…400/50=8
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
AGAIN:
If 8000 calories of energy are added to
200g of water. What is the final water
temp?
40 degrees C
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
AGAIN:
How many calories of energy are needed
to heat 731g of water from 35 to 83
degrees Celcius?
35088 calories
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
LAST ONE:
You add 7000J to 3kg of water that has a
starting temperature of 45 degrees
Fahrenheit. By how many degrees
Fahrenheit does the water temperature
change?
THERE ARE ADDITIONAL
PROBLEMS ON THE NOTES SECTION
OF WEBSITE
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Because of the high specific heat, the temperature of coastal regions, especially islands, are regulated.
During the summer, the water absorbs a lot of the sunlight’s energy and only heats up minimally resulting
in cooler air temperatures. During winter, the water releases the energy warming the air keeping the winters
warmer.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Great Ocean Conveyor Belt delivering heat to the Northern Hemisphere….
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The Great Ocean Conveyor Belt, as you should have learned in Earth Science, is a massive global current that
carries energy from the sunlight at the equator, which is stored as heat in the water, up to the North keeping
North America and Europe much warmer than it would be otherwise. One of the many fears of global warming
is a disruption of this current resulting in colder temperatures in the North and the next Ice Age.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Water helps modulate our body temperature as well. Just like water regulates the temperatures of land
masses, it also helps organisms to resist temperature changes. Once again, the high specific heat of
water means that is takes a great deal of energy to heat it up. Therefore, we can burn a lot of glucose
and fat to move around, but our bodies will not quickly overheat as a result.
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
1. What is the definition of a calorie?
2. You have 30 ml of water and apply 52 cal of energy to it. Assuming a
100% energy transfer, by how many degrees Celsius does the water
change?
3. Ethanol has a specific heat of approximately 0.6 cal/gC. How many
calories would it take to heat 20g of ethanol by 40 degrees C?
4. Why does ethanol have a lower specific heat than water?
5. What is the difference between heat and temperature. Give an example.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Evaporative
COOLING
Heat of Vaporization
Amount of energy (heat) required to turn a substance
from a liquid to a gas.
What can you predict about water’s heat of
vaporization and why do you predict this?
It is relatively high because once again, the waters are
all H-bonded to each other, which must be broken in
order to evaporate.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Evaporative
COOLING
We also use water to cool ourselves down when we
do begin to overheat to maintain a homeostatic level
of 98.6 F. How does this work?
When we overheat, we sweat. The sweat (water, salt
and a bit of urea) sits on our skin. The molecules of
your skin, which are moving too quickly (because
you are overheating) will bump into the water, The
result is your molecules moving slower and the water
speeding up (energy transfer). Some of the water will
move fast enough to jump off of your body
(evaporate), carrying the kinetic energy away with it
thereby cooling you down.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Evaporative
COOLING
If you wanted to cool a person down as quickly as
possible would you use water or isopropanol?
Explain why.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The solid phase of water (ice) floats
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Why does ice float and does this matter in terms of life on this planet?
Ice floats because it is less dense than liquid water. What does that mean?
It means that the water molecules take up more space/volume when water freezes
compared to when it is a liquid (density is mass/volume). The mass is the same, but the
volume is greater. Why is the volume greater?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The volume is greater because when water is cooled down (the molecules slow down) each water
molecule will eventually move slow enough to make the maximum (4) hydrogen bonds with other waters
forming a crystal of water (ice). The crystal has large spaces in it that liquid water doesn’t have making
it less dense. In liquid water, the water molecules are moving quickly and H-bonds are being made and
broken constantly and those large spaces found in ice are filled in making liquid water more dense.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Great, but who cares if ice floats?
Arguably, life would not exist. If ice were more dense, as it forms in winter it would sink making the
bottoms of lakes/oceans/etc… colder and eventually a build up of ice would occur. This ice is deep
enough that even in the summer it would not melt as it would be insulated by the upper layer of
water. The ice would build winter after winter until the oceans/lake would be completely frozen. The
great ocean conveyor belt certainly would not exist and the Earth would be a snowball…
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
euphausid shrimp below arctic ice
Great, but who cares if ice floats?
Therefore, ice is a barrier or insulator against the cold air above and protects
waterways from freezing over allowing life to persist.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The Universal Solvent…adhesion
(Solution, solvent, solute)
Solvent – that which is dissolving the solute
Solute – that which is being dissolved
Solution – the result of a solute being dissolved in a
solvent, a homogeneous mixture
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
The Universal Solvent…adhesion
(Solution, solvent, solute)
Water is referred to as the universal solvent because it can
dissolve a huge number of different substances; all of which are
hydrophilic (contain many polar covalent bonds) and or charged.
Ex. Water can dissolve salts, proteins, carbohydrates, DNA, RNA,
vitamins, minerals, phosphate, nitrate, and the list goes on and
on… All of these molecules are hydrophilic.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
What does it mean to dissolve?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
This is a figure showing
water dissolving a crystal
of sodium chloride, which it
can easily do because the
sodium is positively charged
and the chloride is
negatively charged.
Hydration shell
“Cage” of water molecules surrounding each dissolved substance
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Like Dissolves Like
Water is polar and therefore will dissolve other polar/charged
substances because it can stick to and surround them in solution.
Water cannot dissolve olive oil, because olive oil is mostly non-polar and
therefore it has no charge to interact with and is termed non-polar. The
water will stick to other water molecules excluding the oil, which is why
the oil floats on the water.
However, olive oil can dissolve in other non-polar substances like vegetable oil. They
are both non-polar and therefore neither will stick to the other (ignoring Van der
Waals), but nothing prevents them from mixing together.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
All of the properties we have discussed thus far trace back to…
…charge (H-bonding) and geometry:
Cohesion
Moderation of Temperature
Evaporative Cooling
Adhesion
Universal Solvent
Ice Less Dense than Water
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: What is so important about water?
Which can ultimately be traced back to the number
of protons (reductionist)…
Remember that all of these properties stem from the fact the water
makes hydrogen bonds with 4 other waters due to its geometry,
which is the result of its electron arrangements, and its charge due
to oxygen being more electronegative than hydrogen because it has
8 protons vs. hydrogen’s one proton, and the protons also determine
the electron arrangement. It all goes back to the number of
protons!!!!!
Chapter 3 – Water and the fitness of the environment
NEW AIM: pH?
Concentration
Chapter 3 – Water and the fitness of the environment
AIM: pH?
Aqueous Na+Cl- solutions:
1 liter
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Which solution has a higher concentration of sodium?
**“Aqueous” tells you the solvent is water.
The solution on the left as the concentration is 5 Na+/L compared to the one on the right at 4 Na+/L.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Aqueous Na+Cl- solutions:
1 liter
500 ml
Which solution has a higher concentration of sodium?
The solution on the right as the concentration is 8 Na+/L compared to the one on the right at 5 Na+/L.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Aqueous Na+Cl- solutions:
1 liter
500 ml
Which solution has a higher concentration of water?
If the solution on the right has more Na+ per unit volume then there must be less water per unit
volume. Therefore the solution on the left has a higher concentration of water.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Aqueous Na+Cl- solutions:
1 liter
500 ml
Which solution has a higher concentration of sodium?
The concentrations are equal in this case at 8Na+/L.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Aqueous Na+Cl- solutions:
1 liter
500 ml
Which solution has a higher concentration of water?
Again, they are equal.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity
1 liter
If there were 6.02x1023
sodium atoms, what would
the concentration be?
6.02x1023 sodiums/L = 1 mol / L or… 1 Molar (M)
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
[ ] = concentration
[glucose] = concentration of
glucose
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
If I have a 10M glucose solution, how
many molecules of glucose would I have
in 200ml ?
There would be 10 moles (10 x 6.023x1023) of glucose in 1 L of solution. I took
200ml or 1/5th of a liter. Therefore, 200ml would have 2 moles of glucose or 2 x
6.023x1023 glucose molecules.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Potassium has
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 1L of a 0.7M
KCl solution.
1. Determine the molecular weight (molecular mass) of KCl…
Atomic mass of K = 39.0983 da
Atomic mass of Cl = 35.453 da
Molecular weight (m.w.) of KCl = 74.55 da Which means what?
It means that 74.55g of KCl will be 1 mol of KCl compound….why? Explain.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 1L of a
300mM KCl solution.
1. Determine the molecular weight (molecular mass) of KCl…
Atomic mass of K = 39.0983 da
Atomic mass of Cl = 35.453 da
Molecular weight (m.w.) of KCl = 74.55 da Which means what?
It means that 74.55g of KCl will be 1 mol of KCl compound….why? Explain.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 1L of a
300mM KCl solution.
It means that 74.55g of KCl will be 1 mol of KCl compound….why? Explain.
1. Remember that 1 mol of protons/neutrons = 1g
2. A single KCl on average has 74.55 protons/neutrons.
3. If I have 1 mol of KCl then I have 1 mol of 74.55 protons/neutrons or
6.023x1023 x 74.55 protons and neutrons.
4. Since 6.023x1023 x 1proton or neutron = 1g,
then 6.023x1023 (1 mol) of 74.55 protons/neutrons = 74.55g
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 1L of a
300mM KCl solution.
1. Determine the molecular weight (molecular mass) of KCl = 74.55 da telling us that there are 74.55 g/mol.
2. Weigh out the necessary amount.
You want to make a 300mM (300 milliMolar) solution = 0.3M solution = 0.3mol/L
Therefore you want to weigh out 0.3 moles
74.55g
Xg
=
1 mol
0.3 mol
0.3 mol = 22.4g
X = 22.4g
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 1L of a
300mM KCl solution.
1. Determine the molecular weight (molecular mass) of KCl = 74.55 da telling us that there are 74.55 g/mol.
2. Weigh out the necessary amount.
3. Add 22.4g to 900ml of water and stir
4. Bring volume up to 1 Liter
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 700ml of a
250mM NaCl solution.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Molarity (M)
Explain how you would make 250ml of a
200mM NaCl, 20mM Hepes solution at pH
6.8.
Hepes
Molecular mass (weight; m.w.) = mass of the molecule = 238.3 amu (daltons) for Hepes
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
1. Compare the structure of ice to that of water and use this to explain why
ice floats.
2. How would you make 400ml of a 350 mM NaCl, 10mM Tris solution
with a pH of 8.5. Tris has a molecular mass (weight) of 121 amu.
3. What does it mean to be dissolved in an aqueous solution? For
example, if I through a glucose crystal in water, what does it mean when I
say it dissolved on the molecular level?
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
2. How would you make 400ml of a 350 mM CaCl2, 10mM Tris solution
with a pH of 8.5. Tris has a molecular mass (weight) of 121 amu.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
H2O
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
What is pH, why does such a value exist?
Because a small fraction of water (1 in a billion molecules) in an aqueous solution dissociates:
H2O
H
+
Hydrogen ion
+
-
OH
Hydroxide ion
(aka… a proton)
The oxygen atom is more electronegative than the hydrogens and pulls the shared
electrons away from them, which can cause one of the hydrogens (a proton) to fall off.
This happens to a small number of water molecules in any aqueous solution.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Although it appears that the hydrogen ion is now just diffusing around
in solution, in actuality, what happens to it?
H2O
H
+
+
Hydrogen ion
(aka… a proton)
It will transfer from one water to another to form H3O+.
-
OH
Hydroxide ion
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
What is pH?
H2O
H
+
proton
+
-
OH
Hydroxide ion
pH stands for potential hydrogen and is a measure of the concentration of
hydrogen ions (protons) in an aqueous solution.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
H2 O
+
H
+
-
OH
pH is measured on a logarithmic scale
from 0 to 14.
The higher the H+ (free proton)
concentration, the lower the pH
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Acidic, Basic and neutral
solutions
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Acidic solution
One whose pH is below 7
Basic solution
One whose pH is above 7
Neutral solution
One whose pH is 7
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
What do these pH
values mean in terms
+
of actual
[H
]
values??
(H concentrations)
+
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
What do these pH
values mean in terms
+
of actual
[H
]
values??
(H concentrations)
+
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
pH value
[H+] (M)
=
pH
-log [H ]
+
0
100 = 1M
1
10-1 = 1/10 = 0.1M
2
10-2 = 1/100 = 0.01M
3
10-3
4
10-4
5
10-5
6
10-6
7
10-7
8
10-8
9
10-9
10
10-10
11
10-11
12
10-12
13
10-13
14
10-14
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Logarithms (logs)
The log of a number is simply how many powers of 10
you can pull out of that number.
Ex. log 1000
= 3 because you can pull three powers of
10 out of 1000 (10 x 10 x 10) or 103 = 1000
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Logarithms (logs)
Ex. Log 100,000 = 5 because you can pull out 5 powers
of 10 from 100,000 or 105 = 100,000.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Logarithms
log 103= log 1000 =
2
3
log 104= log 10,000 =
4
log 105=
5
log 106=
6
log 10-1= log .1 =
-1
-2
log 102= log 100 =
log 10-2=
log 10-3=
-3
log 10-4=
-4
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Logarithms
Then if you take the negative
log…
The signs switch
-log 102=
-2
-log 103=
-3
-log 104=
-4
-log 105=
-5
-log 106=
-6
-log 10-1=
1
-log 10-2=
2
-log 10-3=
3
-log 10-4=
4
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
If you have pure water:
+
-
H2O H OH
+
-7
=
=
[H ] [OH ] 10 M
(concentration of “free” protons)
+
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
1. What does pH indicate?
2. Explain why all aqueous solutions have a pH.
3. If I have a solution at pH=3, then the [H+] will be… (don’t forget
units!!)
4. How many more times acidic is a solution at pH 2 compared to pH 5?
5. Why can H+ concentration and proton concentration be used
interchangeably?
5. It’s not really the H+/proton concentration we are measuring, but instead
the ______________ concentration.
Chapter 2 - The Chemical Basis of Life
AIM: What’s the matter?
Quizicule
1. Compare the structure of ice to that of water and use this to explain why
ice floats.
2. How would you make 300ml of a 400 mM NaCl, 10mM Tris solution
with a pH of 8.5. Tris has a molecular mass of 121 amu.
3. What does it mean to be dissolved in an aqueous solution? For
example, if I through a glucose crystal in water, what does it mean when I
say it dissolved on the molecular level?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
+
If you have pure water: [H
log [H ]
=
-7
pH -log [10 M]
=
pH
=
pH 7
+
-7
=
] 10 M
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
+
If you have pure water: [H
-log [H ]
=
-7
pH -log [10 M]
=
pH
pH = 7
+
-7
=
] 10 M
+
What if the [H ] is
10X higher?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
+
-7
=
] 10 M
[H
+
=
pH -log [H ]
=
-7
pH -log [10 M]
=
pH 7
Increase 10 X
+
-6
=
[H ] 10 M
+
=
pH -log [H ]
=
-6
x -log [10 M]
=
pH 6
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
+
-7
=
] 10 M
[H
+
=
pH -log [H ]
=
-7
pH -log [10 M]
=
pH 7
Increase 10 X
+
-6
=
[H ] 10 M
+
=
pH -log [H ]
=
-6
x -log [10 M]
=
pH 6
1. As [H+] goes up, pH goes DOWN
2. As [H+] goes down, pH goes UP
3. A change in 1 pH corresponds to a 10-fold change in [H+]
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
1. What does the pH value tell us about the
solution?
+
2. What happens to the pH as the [H ]
increases?
3. If the pH of a solution is increased by
three pH units, how has the [H+] changed?
The H+ (free proton) concentration [H+]
decreases
1000x lower [H+]
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How many times
more acidic is lemon
juice than urine?
10,000X more acidic
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How many times more
basic is milk of magnesia
(pH 11) compared to
seawater (pH 8)?
1000X more basic
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Acid
vs
Base
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Acid
A substance that when added to a solution
will cause the pH to decrease
Ex. HCl (hydrochloric acid)
HCl -> H+ + ClChlorine is highly electronegative
relative to hydrogen and pull the
shared electrons away causing the
H+ to fall off.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
Base
A substance that when added to a
solution will cause the pH to increase
(decrease the H+ concentration).
Ex) NaOH (sodium hydroxide)
NaOH  Na+ + OHthen
OH- + H+ H2O
The OH- will then grab H+ in the solution
and thereby lower the H+ concentration.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
1. If you add acid to a solution, is that
solution acidic or basic?
You can’t know from this information. If you add acid to a solution with a pH of 11,
you might change it to a pH of 10 (stays basic). If you change it to 6 then it will be
acidic, but you need to know the final pH. Acids and Bases just raise and lower pH,
they say nothing about the solution being acidic or basic.
+
2. Calculate the pH of a solution with an [H ]
-2
of 10 M.
pH = -log[H+]
pH = -log[10-2]
pH = 2
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
pOH
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How does one determine the pH of a solution?
Buffers
A buffer is a chemical (a weak acid or weak base)
that when added to an aqueous solution will allow
the solution to resist changes in pH.
Why are buffers critical in biological systems?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How does one determine the pH of a solution?
Buffers
Example - Let’s say you have carbonic acid in an
aqueous solution:
Response to rise in pH
H2CO3
HCO3- + H+
Response to drop in pH
Carbonic
acid(H+
Base
(H+ acceptor)
donor)
What happens if we add an acid like HCl to this solution?
Le Chatelier's Principle states:
If I add acid (H+) to this solution in the form of HCl, I should push the reaction to the left as
the H+ will combine with HCO3-. The HCO3- is acting like a sponge and absorbing the H+
that I add thereby preventing a pH change.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How does one determine the pH of a solution?
Buffers
Example - Let’s say you have carbonic acid in an
aqueous solution:
Response to rise in pH
HCO3- + H+
H2CO3
Response to drop in pH
Carbonic
acid(H+
Base
(H+ acceptor)
donor)
What if we add a base like NaOH?
Le Chatelier's Principle states:
Likewise, if I add a base like OH-, it will combine with H+. Since I am removing H+, I will push
the reaction to the right and H+ will be generated preventing a pH shift.
Why can’t a strong acid like HCl act as a base?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: pH?
How does one determine the pH of a solution?
Buffers Useful pH Range pKa
Buffers
MES
Bis-Tris
ADA
aces
PIPES
MOPSO
5.5–6.7
5.8–7.2
6.0–7.2
6.1–7.5
6.1–7.5
6.2–7.6
Bis-Tris Propane
BES
MOPS
TES
HEPES
DIPSO
MOBS
TAPSO
Trizma
HEPPSO
POPSO
TEA
EPPS
Tricine
Gly-Gly
Bicine
HEPBS
TAPS
AMPD
TABS
AMPSO
CHES
CAPSO
AMP
CAPS
CABS
6.16
n/a
6.65
6.88
6.80
n/a
6.3–9.5
7.17
7.28
7.50
7.55
n/a
n/a
n/a
8.20
n/a
n/a
n/a
n/a
8.16
n/a
8.35
n/a
8.49
n/a
n/a
n/a
6.4–7.8
6.5–7.9
6.8–8.2
6.8–8.2
7.0–8.2
6.9–8.3
7.0–8.2
7.0–9.0
7.1–8.5
7.2–8.5
7.3–8.3
7.3–8.7
7.4–8.8
7.5–8.9
7.6–9.0
7.6–9.0
7.7-9.1
7.8–9.7
8.2–9.6
8.3–9.7
8.6–10.0
8.9–10.3
9.0–10.5
9.7–11.1
10.0–11.4
6.10
6.50
6.59
6.78
6.76
6.90
n/a
7.09
7.20
7.40
7.48
7.60
7.60
7.60
8.06
7.80
7.80
7.80
8.00
8.05
8.20
8.26
8.30
8.40
8.80
8.90
9.00
9.55
5.97
6.36
6.46
6.54
6.66
6.75
6.8, 9.0
6.90
7.02
7.16
7.31
7.35
n/a
7.39
7.72
6.66
7.63
n/a
n/a
7.80
n/a
8.04
n/a
8.18
n/a
n/a
9.10
9.49
M8250
B9754
A9883
A9758
P6757
M8389
n/a
B9879
M1254
T1375
H3375
D9648
M3295
T9269
T1503
H3137
P3405
T1377
E9502
T0377
G1002
B3876
H6903
T5130
A9754
T1302
A6659
9.36
M2933
B4429
n/a
A3594
P1851
n/a
B6755
B4554
M3183
T5691
H4034
n/a
n/a
T5566
T6066
n/a
n/a
n/a
E0276
T5816
G3915
n/a
n/a
T5316
n/a
n/a
n/a
C2885
M5287
B7535
A8074
A7949
P8203
n/a
B4679 B9410
B6420
M5162
T6541
H7273
D0306
n/a
T0432
T6791
n/a
P7088
n/a
E1894
T9784
G7278
B8660
n/a
T9659
A9074
n/a
A7585
n/a
C8210
Pick your pH…
All of these chemicals on the
left are buffers. Each will buffer
a solution in a different pH
range. For example, if you
wanted to make a solution with
a stable pH of 8, you can add
HEPES. What if you wanted to
make a solution with a stable
pH of 10?
Chapter 3 – Water and the fitness of the environment
AIM: How does one determine the pH of a solution?
How can one determine
?
the pH of a solution
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH paper Indicators:
RED LITMUS PAPER
Aqueous solution applied here
Turns Blue in Basic
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
Litmus is a water soluble mixture of
different dyes extracted from lichens
(composite organism consisting of a
fungal/algae symbiotic relationship)
and applied to paper.
Lichen growing on a tree
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH paper Indicators:
BLUE LITMUS PAPER
Aqueous solution applied here
Turns reD in aciDic
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH paper Indicators:
Hydrion
paper
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH paper Indicators:
Hydrion paper contains a mixture of dyes that will
turn various colors giving a more precise and
quantitative (quantitative – means you can get
numerical data) pH measurement .
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH paper Indicators:
1. Red litmus
paper
2. Blue litmus paper
3. Hydrion paper
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid Indicators:
Liquid indicators can be added to
a sample taken from an aqueous
solution. The color change of the
indicator will reveal the pH.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid Indicators:
1. Phenolphthalein
Phenolphthalein will turn
pink if the pH is above 8. If
the pH is below 8, no color
change is observed.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
PINK
COLORLESS
The structure of the phenolphthalein molecule changes in different pH values. Above pH 8,
it has a structure that reflects pink. Below 8 the structure changes and does not absorb
light. Structure determines function!!
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid
Indicators:
2. Bromothymol Blue
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid
Indicators:
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid
Indicators:
Above pH 7 – blue
Below pH 6 – yellow
Between 6 and 7 - green
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
pH liquid
Indicators:
3. Methyl Orange
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
A pH liquid indicator fo
every occasion
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
How can I use these indicators to
determine the pH of an unknown
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
Use the following data and determine
the pH of Dr. T’s magical elixir:
Indicator Used
resultant
color
Alizarin yellow R:
yellow
Thymol Blue
:
Bromoresol green:
Bromphenol blue:
Thymol blue
:
(base range)
(acid range)
yellow
yellow
purple
?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
Alizarin yellow R:
yellow
Thymol Blue(base range):
yellow
Bromoresol green:
yellow
Bromphenol blue:
purple
Thymol blue (acid range):
?
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
Use the following data and determine
Answer: ~pH 4
the pH of Dr. T’s magical elixir:
Indicator Used
resultant
color
Alizarin yellow R:
yellow
Thymol Blue
:
Bromoresol green:
Bromphenol blue:
Thymol blue
:
(base range)
(acid range)
yellow
yellow
purple
?
Answer: yellow
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: How does one determine the pH of a solution?
Chapter 3 – Water and the fitness of the environment
NEW AIM: Acid Precipitation?
Chapter 3 – Water and the fitness of the environment
AIM: Acid Precipitation?
Factories, power plants, etc… burn fossil fuels and release compounds like sulfur
dioxide (SO2) and mono nitrogen oxides(Nox=NO and NO2), which will react with
water and ozone to form sulfuric acid H2SO4 and nitric acid (HNO3), respectively.
These acids are then dissolve in rain water forming “acid rain” or “acid precipitation”.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: Why
Acid Precipitation?
is pH important?
The normal pH of rain is around 5.5 (acidic). This is because water reacts with CO2 in
the air to form H2CO3 (carbonic acid).
CO2 + H2O
H2CO3
The double arrow means the reaction goes
both ways. Make sure you memorize this
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: Why
Acid Precipitation?
is pH important?
Acid Rain with pH values below 5 can destroy forest and lake ecosystems.
Organisms have evolved to function in a narrow pH range. A drastic change in pH
can cause our proteins to change structure (denature) and not work properly
anymore resulting in death.
Water
and theBasis
fitness
the environment
Chapter 23 -– The
Chemical
of ofLife
AIM: Why
Acid Precipitation?
is pH important?
This shows a statue in Germany that has been decimated by acid rain. The photo on
the left was taken in the 60’s, the one of the right was taken in the 90’s. The statue
itself is hundreds of years old.