Topic 2.
2 Water
Use theories to explain natural phenomena The theory
that hydrogen bonds form between water molecules
explains the properties of water
What are the properties of water on Earth?
70% of Earths surface is covered in water. It is the only planet
where water is found in all 3 states of matter.
How is water distributed on Earths surface?
Only a small amount of water on earth is potable available near the
surface, liquid and safe to drink.
How do we use water?
Domestic use of water for example drinking, cleaning and cooking is relatively small.
Most water is used by nations around the world to make food, energy, and products.
How is water recycled through the ecosystem?
Sunlight drives a process called the hydrologic cycle that moves water between
the atmosphere and Earths surface. The ground naturally filters and stores water.
Is water still a renewable resource?
Is water still a renewable resource?
Is water still a renewable resource?
Although water is renewable, more and more people are seeing their water
resources effected by climate change, aquifer depletion, and pollution. Good,
freshwater has proven to be a limited resource for many.
Why is water important for life on earth?
Water allows our bodies to do what they need to do plants are able to make
food and oxygen and humans are able to break down food and get energy
How does your
body use water?
Water maintains
homeostasis by filtering
out waste, keeping your
body temperature stable,
and carrying nutrients
around your body.
How do we convert inorganic molecules into the materials
needed to do work?
How can we
describe water?
QuaNtitative
observations of
water:
o Mass
o Volume
o Density
o Temperature
How can we
describe water?
QuaLtitative
observations of
water:
o Color
o Texture
o Phase of
Matter
Understanding: Water molecules are polar and hydrogen bonds
form between them
The chemical formula for water is H2O
In each water molecule,
two hydrogen and one
oxygen are joined
together in a covalent
chemical bond.
Hydrogen and oxygen
do not share electrons
equally.
The hydrogen side of water gains a partial positive charge and
the oxygen side gains a partial negative charge. The positive
and negative sides attract each other like magnets.
Draw a mole the electron shell method of water and the
Lewis dot structure. Show areas of partial positive and
partial negative ends using delta symbols. (+, )
Checking your work:
Checking your work: *both are correct
What are the unique properties of water?
We know that living things need water, but HOW does water
support the life in so many different environments on Earth? Why
do bacteria below glaciers encourage us that microbes might even
live beneath the ice caps of other planets?
There is a CAUSE and EFFECT relationship between the
structure of water and its chemical properties.
Water is polar. Hydrogen bonds form.
Living things benefit from this relationship between water
molecules.
Hydrogen bonds form. Water has surface tension.
Understanding: Hydrogen bonding and dipolarity explain the
cohesive, adhesive thermal and solvent properties of water
1. Cohesion
- Water molecules tend
to stick to other water
molecules
- Example: water forms a
bubble on a penny
1. Cohesion
- Water molecules tend
to stick to other water
molecules
- Example: water forms a
bubble on a penny
1. Cohesion
- The cohesiveness of
water is less than the
adhesiveness between
water and the sides of a
graduated cylinder,
causing water to form a
concave meniscus
**Remember the volume of
water should be read from the
bottom of the meniscus
2. Surface Tension
- Water resists being
broken at the surface
where molecules meet
the air
- Example: Basilisk
lizards and water
striders walk on water
2. Surface Tension
- Water resists being
broken at the surface
where molecules meet
the air
- Example: Basilisk
lizards and water
striders walk on water
This is why belly
flops hurt so
much!
2. Surface Tension
- Water resists being broken at
the surface where molecules
meet the air
- Example: Basilisk lizards and
water striders walk on water
2. Surface Tension
- Benefit to living
organisms: Cohesion
of water molecules is
causes surface tension,
which allows insects to
walk along the top
surface of the water,
escape predators,
mate and feed on the
water's surface
2. Surface Tension
- Benefit to living
organisms: Cohesion
of water molecules is
causes surface tension,
which allows insects to
walk along the top
surface of the water,
escape predators,
mate and feed on the
water's surface
Try it at home: Surface tension is why things that should sink
in water paper clips and pepper flakes, will float on the top
until the surface is disturbed.
3. Adhesion
- Water molecules tend
to stick to other
molecules with slight
charges
- Example: Curved
meniscus on a
graduated cylinder
3. Adhesion
- Water molecules tend
to stick to other
molecules with slight
charges
- Example: Curved
meniscus on a
graduated cylinder
3. Adhesion
- Water molecules
tend to stick to
other molecules
with slight charges
- Example: Curved
meniscus on a
graduated cylinder
3. Adhesion
- Water molecules
tend to stick to
other molecules
with slight charges
- Example: Curved
meniscus on a
graduated cylinder
Adhesion CAUSES the concave Meniscus of water
Adhesion CAUSES the concave Meniscus of water
Adhesion is Cohesion is
stronger than stronger than
Cohesion Adhesion
Water Mercury
4. Capillary Action
- As water evaporates,
molecules are pulled
along in a chain while
others appear to climb
the edges of vascular
tubes in plants
4. Capillary Action
- Benefit to living
organisms: Water can
travel against gravity
from the roots to the
shoots of giant
redwood trees!
Try it at home: Adhesion is what causes water to climb up a
paper towel and food coloring to appear to climb up celery
Try it at home: Adhesion is what causes water to climb up a
paper towel and food coloring to appear to climb up celery
Term Mix-up
A solution is a mixture of a solute
(usually solid) dissolved in a solvent
(usually liquid).
A solute dissolves.
A solvent is able to dissolve
another substance.
Most chemical reactions in biology
occur in solutions where molecules
are free to move around and
collide.
5. Universal Solvent
- Water surrounds
and separates
charged molecules
and dissolves many
substances
- Example: Sugar
dissolves in tea
5. Universal Solvent
- Water surrounds and
separates charged
molecules and dissolves
many substances
- Example: Sugar
dissolves in tea
5. Universal Solvent
- Water surrounds and
separates charged
molecules and dissolves
many substances
- Example: Sugar
dissolves in tea
Polarity CAUSES it to be a Universal Solvent
6. Floats as a Solid
- At OoC, water is less
dense than liquid water
because it forms rigid,
hexagonal
arrangements keeping
molecules apart
Hydrogen bonding CAUSES ice to be less dense
Hydrogen bonding CAUSES ice to be less dense
A lower density CAUSES ice to float
Less dense Equal More dense
A lower density CAUSES ice to float
A lower density also CAUSES ice to expand
6. Floats as a Solid
- Benefit to living
organisms: Solid water
rises over lakes and
insulates the
temperature below for
life
Why does ice float in water?
http://ed.ted.com/lessons/why-does-ice-float-in-water-george-zaidan-and-charles-morton
7. Resistance to Temperature Change
- Compared to other
substances, a lot of
energy is needed to
heat one gram of water
one degree Celsius
- Water has a high boiling
point, low freezing
point, and moderates
climates
7. Resistance to Temperature Change
- Compared to other
substances, a lot of
energy is needed to
heat one gram of water
one degree Celsius
- Water has a high boiling
point, low freezing
point, and moderates
climates
Term Mix-up
SPECIFIC HEAT CAPACITY
Hydrogen bonds restrict the motion of water
molecules
Increasing the temperature of water requires breaking
H-bonds, and energy is needed
To cool down water must lose relatively large
amounts of energy
Waters temperature compared to air or land is stable,
making a thermally stable habitat for aquatic life
LATENT HEAT OF VAPORIZATION
The heat needed to separate a molecule as it evaporates
from other molecules in a liquid to become a vapour
molecule
HIGH BOILING POINT
Highest temperature for a liquid state
0 100 degrees C is the temp range for most life on earth
Water molecules move too far apart in vapor to form H-
bonds
What are acids?
In 1661 Robert Boyle summarized
the properties of acids:
1. Sour taste.
2. Corrosive.
3. Change the color of certain
vegetable dyes, such as litmus,
from blue to red.
What are acids?
Acid" comes from Latin acidus,
meaning "sour
Vinegar is a dilute solution of
acetic acid in water
Lemon juice contains citric acid
Milk turns sour when it spoils
because lactic acid is formed
The sour odor of rotten meat or
butter is caused by compounds
such as butyric acid that form
when fat spoils
What are bases?
The properties of bases include
1. Feel slippery.
2. Change the color of litmus
from red to blue.
3. Become less basic when
they are combined with
acids
What are bases?
Boyle defined bases as substances
that consume, or neutralize, acids.
When mixed, bases cause acids to
lose their sour taste, ability to
dissolve metals, and even reverse
the change in litmus paper color.
Alkalies became known
as bases because they serve as the
"base" for making certain salts.
8. Forms Acids and Bases
- Water breaks into H+
and OH ions when
dissolving some
substances
- Water is a mix of
molecules and charged
ions and water breaks
apart into H+ and OH-
- Example: Rain water
can dissolve air
pollution making its pH
lower
Mickey mouse Negative ion Positive ion
shaped water
molecule
Hydrochloric Acid
increases the amount
of H+ ions in a solution.
Acids increase H+
Bases increase OH-
Neutral substances
have equal
concentrations of H+
and OH- ions
Acid Rain
Carbon dioxide
carbonic acid
Sulfur dioxide
sulfurous acid
Nitrogen oxide
nitric acid
pH and Homeostasis
Red Cabbage as a pH Indicator
Understanding: Substances can be hydrophilic or hydrophobic
Hydrophilic = water loving substances that dissolve well in
water
o Examples: salt and sugar
o Like dissolved like water best dissolves ionic or charged compounds
and other polar covalent molecules
Hydrophobic = water fearing things that dont dissolve in
water
o Examples: oil and waxes
o Nonpolar gases that are very small can dissolve by squeezing through
the cracks in water molecules
Amphipathic: a molecule with both hydrophobic and
hydrophilic parts
o Example: The cell membrane forms a phospholipid bilayer (two layers)
o Hydrophilic glycerol heads facing the water/aqueous environment inside
and outside the cell
o Hydrophobic fatty acid tails face inwards and are protected
Micelle = aggregate of
molecules caused by both
hydrophobic and
hydrophilic regions
o Examples: Soap forms a
micelle around dirt
Application: Comparison of the thermal properties of water with
those of methane
Methane: CH4
o Methane is a waste product of anaerobic
respiration in certain prokaryotes
o Found in swamps, wetlands and the guts of
animals such as termites, cattle, and sheep
o Produced in landfills and must be released
to avoid pressure buildup
o Naturally found below the ground and in a
solid state (ice) on the ocean floor
o Strong greenhouse gas contributing to
global warming
Similarities to water
o Small molecules
o Atoms linked by single
covalent bonds
Differences
o Water molecules are polar
and forms hydrogen bonds
o Methane is nonpolar and
does not form hydrogen
bonds
o Water has a higher specific
heat capacity, latent heat
of vaporization, melting
point and higher boiling
point
Application: Use of water as a coolant in sweat
Sweat is secreted by glands
in the skin
The heat needed for the
evaporation of water is
taken from the tissues of
the skin, reducing their
temperature
Solutes, ions like sodium,
are left on the skin Water helps
Regulated by the our bodies
hypothalamus (also maintain
homeostasis
triggered by adrenalin) or balance
with sweat!
Application: Modes of transport of glucose, amino acids,
cholesterol, fats, oxygen and sodium chloride in blood in relation
to their solubility in water.
Metabolic reactions happen most readily in solutions of
water
o Cells are mostly water
o Diffusion into and out of cells occurs more easily if
substances are dissolved in solutions
Blood transports substances in solution to meet the bodys
needs
o Glucose is polar and water soluble
o Amino acids have varying solubility depending on their R group, but all
are able to dissolve in blood plasma
o Fats are large and nonpolar and must be carried in lipoprotein
complexes
- Phospholipid monolayer
o Cholesterol are small, but mostly hydrophobic and must also be
carried in lipoprotein complexes
o Fats are large and nonpolar and must be carried in lipoprotein
complexes
- Phospholipid monolayer
o Cholesterol are small, but mostly hydrophobic and must also be
carried in lipoprotein complexes
o Oxygen is nonpolar but small
enough to dissolve in water
at low concentrations and
low temperatures
- Hemoglobin has an O
binding site
- Hemoglobin increases the
bloods ability to dissolve O
at high enough levels for
aerobic cell respiration
o Sodium Chloride is ionic, soluble in water and carried in blood plasma
Application: There are challenges for increasing the human
population in sharing water resources equitably for drinking and
irrigation, electricity generation and a range of industrial and
domestic processes.
http://www.un.org/sustainabledevelopment/water-and-sanit
ation
/
Application: Claims about the memory of water have been
categorized as pseudoscientific. What are the criteria that can be
used to distinguish scientific claims from pseudoscientific claims?
http://
www.nature.com/news/2004/041004/full/news041004-19.html
How polarity makes water behave strangely
http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg
What is the origin of water on Earth?
The chemical makeup of water allows scientists to evaluate
hypotheses for the origins of earths water, from the formation of
earth to extraterrestrial impacts.
Isotopes of Hydrogen
Isotopes: one forms of atom of the same element, where the
nucleus has the same number of protons, but a different number
of neutrons
o Isotopes can be noted by the element symbol and a dash with the
atomic mass or by placing the atomic mass in the top left hand
corner of an element
o Example: C-14 is an isotope of C-12 with two added neutrons (also,
12
C and 14C)
Radioactive: atoms with unstable nuclei that spontaneously
decay, emitting energy in the form of alpha particles, beta
particles or gamma rays that may be harmful
Hydrogen has three naturally occurring isotopes that are given
names each has a single electron in a single energy orbital
outside the nucleus & behave similar chemically or will interact
with other atoms similarly based on this electron configuration
Protium: (1H or H-1) 1 proton and 0 neutrons in the nucleus
99.98% of H on earth, very stable
Deuterium: (2H orH-2) 1 proton and 1 neutron in the nucleus
Stable - not radioactive or hazardous
Found in oceans more than atmosphere heavy water
Tritium: (3H or H-3) 1 proton and 2 neutrons in the nucleus
Radioactively decays half life = 12.5 years
Fission is a process of splitting atomic nuclei that occurs in
nuclear reactors
Fusion is the process of combining smaller nuclei to form larger
nuclei that occurs on the sun
When deuterium & tritium nuclei fuse, they form a He nucleus, a
neutron & a lot of energy
