Thanks for asking!
There is a distinct difference between chemical reaction and process.
The water cycle involves several chemical processes, which are
influenced by specific chemical reactions, however, the exact nature
of those reactions depend upon specific conditions. A single page
tutorial on Chemical Reactions explains the general principles. A
strict definition of a chemical reaction is one that results in the
making or breaking of chemical bonds.
The Chem Site - Types of Chemical Reactions
http://chem.neopages.com/tutorials/rxn.shtml
These three chemical reactions are present in various phases of the
water cycle. Precipitation reactions occur in the infiltration,
evaporative, and runoff phases, as water molecules come into contact
with various solutions and solids, or as they pass into a gaseous
state, leaving a precipitate behind.
Acid-base reactions in water involve the dissociation of one hydrogen
atom from its electronegative hetereoatom, oxygen.
H2O --> H+ + OH-
This reaction can occur in the condensation phase resulting in the
formation of ozone, the infiltration phase, as water mixes with soils,
the runoff phase, as individual water movement, such as in underwater
rivers and gyres generate new water solutions, and in the evaporative
phase, as molecules of water bond with airborne particulate matter to
form water vapor particles, acid rain, for example.
Wikipedia - Acid-base Reaction Theories
http://www.wikipedia.org/wiki/Acid-base_reaction_theories
The third type of chemical reaction involving aqueous solutions is the
oxidation-reduction reaction. In the water cycle, this occurs most
frequently when water comes into contact with the element iron during
the infiltration and/or runoff phases. Corrosion, or rust, results
from that oxidation reaction.
Kapi'olani Community College - Oxidation-Reduction Reactions
http://library.kcc.hawaii.edu/external/chemistry/
PHASE DEFINITIONS
**********************************************************************
Condensation - Occurs when pressure builds into moisture, and that
moisture passes through the atmosphere and forms into precipitation. A
"state of matter" transition.
Precipitation - Water or ice that condenses in the air and falls to
the ground as rain, snow, sleet or hail. When temperature changes
dramatically, the clouds attempt to adjust their own temperature, and
they either produce rain, snow, sleet or hail. A "state of matter"
transition.
Runoff: Water that does not soak into the ground or evaporate. Excess
water that moves along the earth's surface until it finds a path to
an underground aquifer or to the oceans.
Infiltration: Water that has found a crack or crevice to seep into.
Groundwater often flows as freely underground as it would above
ground.
Evaporation - Heat turns water into water vapor (steam) and the vapor
rises into the atmosphere. A "state of matter" transition.
CHEMISTRY OF WATER - Wikipedia
**********************************************************************
A general explanation of the Chemistry of Water, including properties
and common processes is available from Wikipedia. I have quoted a
short excerpt of basic properties here, however the Wikipedia text
offers many links to related concepts and explanations.
"Water is a simple chemical compound that is liquid at room
temperature and pressure. It has the chemical formula H2O, meaning
that one molecule of water is composed of 2 atoms of hydrogen and one
atom of oxygen. Water is found almost everywhere on earth and is vital
to all known living organisms. About 70% of the earth's surface is
covered by water.
The solid state of water is known as (water) ice; the gaseous state is
known as steam. The units of temperature (formerly the degree Celsius
and now the Kelvin) are defined in terms of the triple point of water,
273.16 K (0.01 °C) and 611.2 Pa, the temperature and pressure at which
solid, liquid, and gaseous water coexist in equilibrium."
Further sections explain properties and processes which add to an
understanding of the behavior of water during the water cycle:
-- The dipolar nature of water
-- Water as a solvent
-- Cohesion and surface tension
-- Conductivity
-- Electrolysis
Chemistry of Water
http://www.wikipedia.org/wiki/Water
STATES OF MATTER AND TRANSITIONS
**********************************************************************
During the hydrologic cycle, water may change matter states from
liquid to gas, or liquid to solid. Each of these H20 transitions is
based upon temperature change. The transitions are:
Fusion (melting): Solid > Liquid (ice > water in the runnoff phase)
Chemical Formula: Heat of fusion, (Delta) Hfus, is enthalpy change at
the melting point of the solid.
Sublimation: Solid > Gas
Evaporation: Liquid > Gas (liquid to vapor in the evaporative phase)
Also known as vaporization. The energy to vaporize 1 mole of a liquid
at 1 atm is the heat of vaporization, Delta Hvap.
Condensation: Gas > Liquid (vapor to liquid in condensation phase)
ADDITIONAL CHEMICAL PROCESSES WITHIN THE WATER CYCLE
**********************************************************************
By no means an exhaustive listing.
Capillary action: the action by which the surface of a liquid where it
is in contact with a solid (as in a capillary tube) is elevated or
depressed depending on the relative attraction of the molecules of
the liquid for each other and for those of the solid. Seen in
transpiration phase.
Crystallization: evaporation of water from a saturated solution
causing the salt or other dissolved solid to crystallize. Seen in
evaporative phase.
Filtration: filtering and purification of water as it moves from the
surface to underground aquifers.
FURTHER STUDY
**********************************************************************
Aqueous Chemistry - Water Cycle
http://www.wpbschoolhouse.btinternet.co.uk/page01/AqueousChem/AqueousChem.htm
Hydrologic Cycle
http://www.uwsp.edu/geo/faculty/ritter/geog101/modules/hydrosphere/hydrologic_cycle.html
Environmental Chemistry (requires Adobe Acrobat Reader)
http://blue.butler.edu/~oakinbo/lecture2.pdf
The Chemistry of the Oceans (requires Adobe Acrobat Reader)
http://www.chemsoc.org/pdf/LearnNet/rsc/oceans.pdf
Rainwater Chemistry and the Sulphur Cycle (again, Acrobat Reader)
http://www.geology.fau.edu/course_info/spring03/GLY5243/5243LN06_S03.pdf
**********************************************************************
Google Search Terms
condensation chemistry
evaporation chemistry
transpiration chemistry
infiltration OR runoff chemistry
geologic chemistry
aqueous chemistry
"water cycle" OR "hydrologic cycle" chemistry
I hope this provides the information you're seeking. Should you have
any questions about the materials or links provided, please, feel free
to ask, and I will assist as needed.
--larre |
