Transcript Temperature stabilizing capacity specific heat of water is 1 cal/gram

Water
A bit about water . . . .
I. Water and hydrogen bonding
II. Properties of water
III. Acids and bases
Water and hydrogen bonding
• Polar covalent bond : bond in which
electrons are shared unequally.
Hydrogen
bonds
Properties of water
•
•
•
•
Cohesion
Temperature stabilizing capacity
Insulation of bodies of water by ice
Solvent properties
Cohesiveness
Due to H-bonding, water is highly
cohesive. Cohesiveness accounts for
high surface tension
Cohesiveness
Water-conducting cells
100 µm
Water and Temperature
Temperature stabilizing capacity
Specific heat - amount of energy a
substance must absorb per gram to
increase temp 1 degree C
Temperature stabilizing capacity
Specific heat - amount of energy a
substance must absorb per gram to
increase temp 1 degree C
specific heat of water is 1 cal/gram
Specific heat of water is higher
than most other liquids because
of extensive H-bonding
Water and
temperature
Effect of a large body of water on temperature
High specific heat
buffers against
temperature
increases
High specific heat of water
Important in context of cell biology because
cells release large amounts of energy
during metabolic reactions.
Release of heat would pose overheating
problem were it not for high specific heat
of water
Evaporative Cooling
Ice Floats
Solvent of Life
Solvent properties
Water is an excellent
solvent for biological
purposes because of its
ability to dissolve great
variety of solutes.
Hydrophilic
Hydrophobic
Solvent properties
• Hydrophilic: polar molecules that dissolve
readily in water; sugars, organic acids, some
amino acids.
• Hydrophobic: non-polar molecules that are not
very soluble in water. lipids, some proteins
Water is a polar
solvent
Water Disassociates
H+
OH -
Acids and bases
• pH scale expresses hydrogen ion (H+)
concentration in a solution.
– logarithmic scale ranging from 0-14
• neutral = 7
pH
• Acids dissociate in water to increase the
concentration of H+.
– pH values lower than 7
• Bases combine with H+ ions when
dissolved in water, thus decreasing H+
concentration.
– pH values above 7
more
H+
more
OH-
pH scale
9
8
7
•Buffers act as a reservoir for hydrogen
ions, donating or removing them from
solution as necessary.
pH
6
Buffering
range
5
4
3
2
1
0
0
1
2
3
4
Amount of base added
5
Acid Precipitation
Coal
Damage from Acid Rain