Section 2.1 - The Role of Water Cycles in Matter
Key terms: biogeochemical cycles, hydrologic cycle, polar, hydrogen bond, cohesion, adhesion
Terms/Focusing
Questions
Content
What elements are
necessary to life?
Water, oxygen, carbon, sulfur, nitrogen, phosphorous
BIOGEOCHEMICAL CYCLES
Bio - life/living, geo - of Earth, chemical - relevant elements, cycle circular path
Def. The routes that water and other chemical nutrients take through the
biotic and abiotic components of the biosphere.
Biosphere - all the areas on Earth (in the air, land, and water) that
are inhabited by and that support life
Can you give an example
of how one of the
elements above can travel
great distances?
HYDROLOGIC CYCLE
The name of the cycle for WATER is the hydrologic cycle. (pg. 35)
Walking water demo
Describe the processes
involved in the hydrologic
cycle in a brief paragraph,
beginning and ending with
water storage in the
atmosphere.
Water is stored in the atmosphere in all three phases. When water
vapour condenses, water falls as precipitation as rain and snow.
Precipitation may be stored as ice or snow, infiltrate the ground to be
stored as groundwater, or enter fresh/saltwater bodies. Water stored as
ice or snow eventually melts and runs off into ground or surface water
bodies. Plants take up water from the soil and return it to the
atmosphere via transpiration. (Animals also take up water and lose it to
the atmosphere.) Water evaporates from the soil, oceans, and other
water bodies. Following these various pathways, water returns to the
atmosphere for storage, completing the cycle.
What are some unique
properties of water?
● Universal solvent (A)
● Relatively high boiling and melting points (B)
● Adhesive and cohesive properties (C)
● High heat capacities (D)
Video - How polarity makes water behave strangely
(A) Water as a universal
solvent.
DO ON YOUR OWN (pg. 35-36)
What is a UNIVERSAL SOLVENT?
A solvent is a substance that dissolves other substances into itself - it
does the action of dissolving. Universal means that it dissolves almost
every substance in the biosphere, good and bad …
POLARITY
What property of water makes it a UNIVERSAL SOLVENT? Describe this
property.
Water is polar, like a magnet with N and S poles. This polarity allows it to
dissolve substances.
Polarity of water demo
Salt dissolving
Draw:
HYDROGEN BONDS
Explain why water is POLAR.
Water is a molecule of one oxygen atom and two hydrogen atoms in a
“V” shape. Since the hydrogens are cations - or positively charged within
the molecule - and since they are on the same side, they create a
positive pole. The oxygen is anion - or negatively charged - forming a
negative pole.
What type of BOND does water’s POLARITY create between other water
molecules or solutes? Describe this BOND in terms of how water
dissolves solutes.
Water’s polarity allows for the formation of hydrogen bonds. This is a
weak bond between hydrogen of one molecule and oxygen of another
molecule (or negative ion). This bond pulls solutes apart into their
elemental ions; this is the action of dissolving.
(B) Water has a relatively
high boiling point and
melting point.
Water freezing
Why does ice float?
TED-ED Ice floats
Explain how the HYDROGEN BOND allows water to stay as a LIQUID over
a large temperature range.
As a liquid, the hydrogen bonds form, break, and reform frequently. This
requires more energy input to break many bonds to boil water. Thus,
molecules in water are packed together quite closely in this phase. They
continue to pack together closer as the temperature decreases until
water reaches its greatest density (1kg/L) at 4 °C.
Explain how the HYDROGEN BOND allows ice to float.
Unlike the solid and liquid states of most other substances, ice is less
dense than liquid water. When water freezes, it expands because
hydrogen bonds hold the water molecules in an open crystal structure.
This prevents the water molecules in ice from getting as close to each
other as they do in liquid water. This expansion begins as the
temperature decreases below 4 °C.
How does hydrogen
bonding affect nutrient
cycling?
(C) Water has adhesive
and cohesive properties
ADHESION
COHESION
How do
adhesion/cohesion affect
transpiration?
Explain the role of HYDROGEN BONDING in:
● Transporting nutrients over a large temperature range:
Universal solvent: dissolves nutrients
High specific heat capacity: constant internal
temperature for animals that have a high concentration
of water in its tissues
● Nutrient cycling in lakes:
Universal solvent: dissolves nutrients
Density: changes in density with changes in temperature
allow for higher density water to sink and be replaced by
lower density water
Define ADHESION: attraction to other molecules
Define COHESION: attraction between water molecules
Explain the role of ADHESION and COHESION in:
● Surface tension:
the attraction of water molecules to each other allows
for many insects to walk on water as well as keep organic
debris on the water surface where it provides nutrients
for aquatic organisms
● Transpiration:
The attraction to both the walls of the xylem (adhesion)
and each other (cohesion) allows water to counteract
gravity as it moves up the xylem to replace water that
has evaporated from the leaves via transpiration.
Beaker-yarn demo
(D) Water has a high heat
capacity
How does water’s high
heat capacity benefit the
biosphere?
Define HEAT CAPACITY: measure of the amount of heat energy a
substance can absorb or release for a given change in temperature
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How do organisms gain
and lose water?
Individual level: Allows life to maintain a fairly constant
internal temperature
Ecosystem level: Oceans and lakes moderate the air
temperature near land
Global level: Surface currents distribute heat from warm
equatorial regions to colder latitudes
Gain water
Lose water
eating
breathing
drinking
sweating
absorption (through skin)
Waste (urine and feces)
metabolic water
What is metabolic water?
Metabolic water is the water created through cellular processes
(metabolism).
Summary: biogeochemical cycles allow nutrients that are key to life to cycle throughout the globe;
water is an example of one of those important nutrients (hydrologic cycle); water is an incredibly
significant nutrient for living things due to 4 main characteristics: universal solvent, high
boiling/melting points, cohesion and adhesion, and high heat capacity
Crash Course Hydrologic Cycle (0-5:13)
DO: Thought Lab 2.1 - Water Gains and Losses
Video - Droughts in the Canadian Prairies
Why is water important?
Define Water Quality: how inundated water is with toxic chemicals or
pathogens
Water quality is important for:
● Society:
● Ecosystems:
Do: Section 2.1 Review, pg. 40 Q 4, 5, 7, 8