Download water,acids,bases,buffers note outline

Biology 12
Note Outline: Water, Acids, Bases and Buffers
A. Basic Chemistry of Water
1. The molecular formula of water is:________________
2. Two ______________ bonds (i.e. chemical bonds in which electrons
are _____________) bind the two ________________ atoms to
the ___________________ atom.
3. Since these two ________________ bonds are found within the
water molecule, their location is described as
_________________.
4. Although the ____________ and _____________ atoms in a
water molecules share ___________________, this sharing is
uneven since ________________ has a greater affinity for
__________________ than _____________________ atoms
do.
5. Therefore, the shared ____________________ spend more time
around the _______________ atom than they do around the
_______________ atoms.
6. Thus, the ___________________ atom has a partial
______________ charge while the
__________________________ atoms have a partial
________________ charge.
7. Since the water molecule has opposite partial charges at either end,
it is described as a ________________ molecule.
Molecular Structure of Water (labeled diagram)
8. Due to the attraction bewteen opposite charges, the partially positive
___________ end of one water molecule will be attracted to the
partially negative ______________ end of another water molecule
which creates weak _______________ bonds between the water
molecules.
9. Since these weak ______________ bonds are found between the
water molecules, their location is described as ______________
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Hydrogen Bonding Between Water Molecules (labeled diagram)
10. The ________________ bonding between water molecules gives
water a number of important characteristics which include the
following:
a. Water has a high heat ____________ (or specific heat)
which means water can absorb a large amount of _________
energy with a minimal change in temperature.
b. Water has a high heat of ____________________ which
means that it takes a large amount of _______________
energy to convert water from a liquid to a ____________.
c. Water has a high _______________ ________________
(or strong cohesion) holding water molecules together.
d. When water freezes, the water molecules arrange themselves in
a very organized ________________ structure in which the
average distance between molecules is______________ than
that of liquid water. Therefore, ice is less ________________
than the liquid water.
11. In pure water (eg distilled water) a small number of water molecules
dissociate (split up) into ____________________ ions (H+) and
____________________ ions (OH-).
B. Biologically Significant Properties of Water
1. Effective Polar Solvent
 Solutions consist of two parts:
i. The _________________ which is the liquid part of a
solution
ii. The _______________ which is the solid part of the
solution and is dissolved in the _________________.
 In the solutions found in organisms (cytoplasm, blood, lymph)
the solvent is always ________________.
 There are a wide variety of solutes found in organisms (salts,
amino acids, glucose etc.) which are mostly ______________
molecules.
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
2.
3.
4.
5.
_______________ solutes are best dissolved by
_______________ solvents.
 Since water is a _______________solvent, it is able to
dissolve the many __________________ solutes found in
organisms.
High Heat Capacity/Specific Heat
 Due to intermolecular ______________ bonding, water
has a _________________ heat capacity.
 Therefore, the water found in the solutions of organisms is able
to absorb a large amount of ______________ energy with a
minimal change in ____________________.
 This helps to maintain a relatively stable internal
__________________ within organisms
 Since the external environment of organisms contains a large
amount of water (water vapour, oceans, lakes etc) the water’s
__________ heat capacity helps to maintain a realatively
stable external __________________ around the
organisms.
High Heat of Vaporization
 Due to intermolecular _____________________
bonding, water has a ______________ heat of vaporization.
 Therefore, water in the form of ________________ is an
effective cooling agent in humans since the water absorbs a lot
of body heat as it ___________________.
High Surface Tension/Cohesion
 Due to intermolecular _______________ bonding, water
has a ________________ surface tension.
 This helps to ensure that surfaces in organisms that must be
kept moist in order to function properly (mucous membranes)
will have a continuous layer of _______________ over them.
Ice is Less Dense than Liquid Water
 Due to intermolecular ___________________ bonding,
when water freezes it forms an organized
____________________ structure which is less dense than
liquid water.
 Thus, ice floats, insulating the organisms living in the liquid
water below from the extremely low ________________ in
the air above.
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C. pH, Acids, and Bases
1. pH
 pH is a measure of the ________________ ion concentration
[ H+] of a solution.
 The pH scale runs from _________ to ___________
 Since the pH scale is a logarithmic scale, there is an
____________ relationship between the pH number and the
_______________________
 Thus, the lower the pH number, the ____________ the [ H+]
Example: A solution with a pH = 3 has a
___________________ [ H+] than a solution with a pH = 12
2. Acidic Solutions
 An acid is a substance that dissociates (splits up) in water and
________________ the hydrogen ion concentration of the
solution.
Example: HCl
H+ + Cl –
 Since hydrogen ions are simply protons, acids can be called
__________________ donors.
 By _______________ the hydrogen ion concentration, acids
_______________ the pH of a solution.
 Therefore, acidic solutions have a pH which is ___________
than 7.
 Thus, acidic solutions have a _______________ [ H+] and a
low _______________ number.
 When [ H+] in a solution is high, the hydroxide ion
concentration [ OH-] will be ________________.
 Therefore, in acidic solutions, the hydrogen ion concentration is
__________________ than the hydroxide concentration.
3. Basic Solutions
 A base is a substance that dissociates in water and
__________________ the hydroxide ion concentration of
the solution.
Example: NaOH
Na+ + OH The ________________ ions from a base can combine with
hydrogen ions (protons) to form _______________.
 Therefore bases are sometimes called _________________
acceptors.
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
Since bases__________________ the [ H+] of a solution,
they __________ the pH of the solution.
 Therefore, basic solutions have a pH which is
______________ than 7.
 Thus, basic solutions have a __________________ [ H+] and
a _______________ pH number.
 In basic solutions, the [ H+] is _______________ than the
[OH-].
4. Neutral Solutions
 In an neutral solution (water), the pH =________
 In a neutral solution, the [ H+] is ___________ to the [ OH-]
 Acidic solutions can be neutralized by adding a
_____________ while basic solutions can be neutralized by
adding an ______________.
5. Buffers
 Buffers are compounds which are capable of stabilizing the
___________ of a solution by combining with excess
___________ ions or _____________ ions.
 An example of a buffer which helps to maintain the pH of the
blood in humans is ______________.
6. Simple pH calculations
 pH formula: pH= -log[ H+]
 [ H+] and [ OH-] relationship
i. In all solutions, [ H+] and [OH-] have the following
relationship: [ H+] x [ OH-] = 1 x 10-14 M\
Examples:
 If pH = 4 then [ H+] = 1 x 10-4 and [ OH-] = 1 x 10-10
 If pH = 12 then [ H+] = __________ and [ OH-]= __________
 If pH = 9 then [ H+] = ___________ and [ OH-]= __________
 If [ H+] =1 x 10-8, then pH = 8 and [OH-] = 1x10-6
 If [ H+] = 1 x 10-2 ,then pH = _______ and [ OH-]= __________
 If [ OH-] = 1 x 10-3 ,then [ H+] = 1 x 10-11 and pH = ___________
 If [ OH-] = 1 x 10-14 , then [ H+] = ____________ and pH = ______
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