2.2 Water
IB Biology HL 1
Mrs. Peters
Fall 2014
U 1. Water

2 Hydrogen atoms +
1 Oxygen atom
covalently bonded
(polar)
 Makes up 70-95% of
living things, covers
75% of Earth
 DRAW and LABEL
this in your notes,
showing polarity
Red: oxygen
White: hydrogen
U1. Hydrogen Bond Formation
Hydrogen bonds form
between water
molecules
•Weak intermolecular
forces
•Attraction between the
slightly positive H and
the slightly negative O
of different water
molecules.
•Always represented
by a dotted line.
•Draw in your notes!
U 2. Properties of Water

Cohesion



created by the constant forming and reforming of
hydrogen bonds between water molecules
Enables water to move against gravity for transport in
plants
Creates surface tension
U 2. Properties of Water

Surface Tension



A measure of how difficult it is to stretch or break the
surface of a liquid
Created by the cohesive property of water molecules
Water has a greater surface tension than most other
liquids
U 2. Properties of Water
Adhesion: waters ability to adhere to other
polar molecules by forming hydrogen bonds
Useful in plants: absorption of CO2 for
photosynthesis in leaves
glogster.com
Landryamps.com
U 2 Thermal Properties of Water
 High


Specific Heat Capacity
Can absorb or give off heat energy without
changing temperature very much due to the
breaking and forming of hydrogen bonds.
The amount of energy required to change the
temperature of water is relatively high
U 2 Thermal Properties of Water
 High
Specific Heat Capacity
• Allows organisms to maintain a constant
temperature
• Also acts as a temperature regulator within
the body (blood moves warmer blood to
cooler parts of the body)
U2 & A2. Thermal Properties of
Water

High latent heat of
Vaporization:
transformation from liquid
to gas



Water absorbs a great deal
of heat when it evaporates
Used as a cooling
mechanism
Creates sweat in animals
and transpiration in plants
U2. Thermal Properties of Water

High Boiling Point



Highest temperature reached in liquid state
High due to amount of energy required to break Hbonds.
Water stays a liquid over a broad range of
temperatures (0-100oC), which is most habitats on
Earth
Solarviews.com
Background Info: Parts of Solutions

Solution: a liquid
mixture of 2 or more
substances
 Aqueous solution:
liquid in which water
is the solvent
Background Info: Parts of Solutions

Solvent: dissolving
agent of solutions
 Solute: substance
being dissolved
U2. Solvent Properties of Water
 Solvent


Water’s polarity helps dissolve ions and other
polar substances (like dissolves like)
Creates an excellent medium for transporting
substances around the body
U2. Solvent Properties of Water
 Solvent

Excellent medium for metabolic reactions to take
place
•
•
•
•
Cytoplasm: glycolysis, protein synthesis reactions
Nucleoplasm: DNA replication, transcription
Stroma: light reactions of photosynthesis
Blood Plasma: loading and unloading of respiratory
gases; clotting
U2. Solvent Properties of Water
 Solvent

Examples
Plants: vascular tissue carries water and
dissolved substances
• Xylem carries water and minerals from roots to leaves
• Phloem carries dissolved sugars from leaves to stems,
roots and flowers
Diffen.com
U2. Solvent Properties of Water
 Solvent

Examples
Animals: blood is the most common transport
medium, largely made up of water (blood plasma)
• Transports: red blood cells, white blood cells, platelets,
dissolved molecules (glucose, amino acids, salts, urea)
U2.Common Aqueous Solutions
Aqueous Solution
Location
Common Reaction
Cytoplasm
Fluid inside cells but
outside organelles
Fluid inside nuclear
membranes
Fluid inside
chloroplast
membranes
Glycolysis
Protein synthesis
DNA replication
Transcription
Light independent
reactions of
photosynthesis
Fluid in arteries, veins,
and capillaries
Loading and unloading
of respiratory gases
Blood clotting
Nucleoplasm
Stroma
Blood Plasma
U3. Substances can be hydrophilic

Hydrophilic:
 “Water loving”
 any substance with
an attraction to water


Substance does not
have to dissolve
EX: glucose, sodium
and chlorine ions,
other polar substances
U3. Substances can be hydrophobic

Hydrophobic:
 “water fearing”
 any substance which
repels water or
insoluble in water

Ex: l]hospholipids,
fatty acids, oils, nonpolar molecules,
methane, prop
A3. Transportation of Molecules
Substance
High or low relative
solubility in water
Mode of transport in an aqueous
environment (no special mode
means the substance dissolves
directly and easily into water)
Glucose
Polar molecule/ high
solubility
No special mode of transport
needed, dissolves directly into
plasma
Amino Acids Varying polarity but all are
reasonably soluble
No special mode of transport,
dissolve directly into plasma
Cholesterol
Transported by blood proteins
with polar amino acids on the
outside to give water solubility,
non-polar amino acids internally
bond to non polar cholesterol
Largely non-polar, very
low solubility
A3. Transportation of Molecules
Substance
High or low relative
solubility in water
Mode of transport in an aqueous
environment (no special mode
means the substance dissolves
directly and easily into water)
Fats
Non-polar fatty acid
components, very low
solubility
Transported by blood proteins
with polar amino acids on the
outside to give water solubility,
non-polar amino acids internally
bond to non polar fatty acids
Oxygen
Travels as O2, low
solubility
Relatively low solubility in water
and warm temps., haemoglobin
is used to bind and transport
oxygen
Sodium
Chloride
Ionizes, high solubility
No Special mode of transport
needed, separates into Na+ and
Cl- ions in plasma
U2. Water Properties Review
Property
Cohesion
Reason
Hydrogen bonds hold water
molecules together
Consequence
Water can travel in continuous
columns; act as a transport
medium
Solvent
Polar molecules of water can
Able to dissolve ions and large
interact with other polar molecules molecules with polar side chains;
acts as an excellent transport
medium and medium for
metabolic reactions
Thermal
Water has a high heat capacity
(lots of energy needed to break H
bonds and change temp)
Organism temp changes slowly;
body fluid (blood) transports heat
throughout
Thermal
Water has a high boiling point
(lots of energy needed to break H
bonds)
Liquid at most temps life exists;
medium for metabolic
reactions
Water has a high latent heat of
vaporization as H bonds break
acts as a coolant (sweating in
animals and transpiration in
plants)
Thermal