Chemistry In The Environment: Water
1/18 Assignment: DHMO Read the article on DHMO.Discuss in your
groups the answers to the following questions.In your notebook ,
write the answer to these questions. You must write in complete
sentences but dont have to write the question.1) Should DHMO be
banned. Give a reason why or why not?2) What are two hazards of
DHMO and two benefits of DHMO to humans?3) What chemical do you
think DHMO is?1/18 HomeworkFill out the information on the back
page of your syllabus and have your parent or gaurdian sign it.
Return the assignment to Mr. O by next Wednesday.
(10 pts)
Chemistry In The Environment: WaterDistribution of WATER70.9% of
the Earths surface is covered by water.Oceans hold 97% of surface
water.Glaciers and polar ice caps hold 2.4%Rivers, lakes, ponds and
groundwater holds contains the remaining 0.6%A very small amount of
the Earths water is contained within biological bodies and
manufactured products.We need freshwater!!!!Only 2.5% of water on
the Earth is fresh water, and over two thirds of this is frozen in
glaciers and polar ice caps.
Water demand already exceeds supply in many parts of the world,
and many more areas are expected to experience this imbalance in
the near future
WHAT PROPERTIES OF WATER MAKE IT ESSENTIAL FOR LIFE ON
EARTH?Chemical and Physical PropertiesWater is liquid at STP. It is
tasteless and odorless.
All 3 common states, solid, liquid and gas appear in nature.
Physical and Chemical PropertiesClean drinking water is
essential to humans and other life forms. Humans and other animals
have developed senses which enable them to evaluate the potability
of water by avoiding water that is too salty or putrid.
Water is transparent in the visible electromagnetic
spectrumAquatic plants can live in water because sunlight can reach
them. Ultra violet and infrared light is strongly absorbed.
Water is a polar molecule (unequal sharing of electrons) with a
bent shape.
This causes strong attractive forces between molecules of water.
Allowing it to have high surface tension and capillary forces.
Water is a Universal SolventHYDROPHILIC (water loving) Substances
that dissolve in water like salts, sugars, acids, alkalis and some
gases like oxygen and carbon dioxide.HYDROPHOBIC (water
fearing)Substances that do not mix well with water such as fats and
oils.All the major components in cells are dissolved in water
Other fun facts about water!!!Pure water has a low conductivity.
The boiling point of water is dependent of the barometric pressure.
Water on the top of Mt. Everest boils at 68o C compared to 100oC at
sea level.
Why does ice float?The maximum density of water occurs at
3.98oC.
As water freezes it expands to occupy 9% greater space in its
solid form that in its liquid state.
How does water help moderate temperature?Earth is a complex and
dynamic system with a surface that is more ocean than land.
The ocean interacts continually with the atmosphere, by
exchanging, storing, and transporting matter and energy.
Water bodies have a much higher heat capacity than land and
intercept more incoming sunlight than land surfaces because of its
greater transparency. How is clean fresh water produced in
nature?
The Water Cycle (Hydrologic Cycle)The water cycle refers to the
continuous exchange of water within the hydrosphere between the
atmosphere, soil, water, surface water , groundwater and
plants.
EvaporationSolar energy strikes the ocean water causing water
molecules to escape from the liquid and rise as gas
TranspirationPlants lose moisture through small holes in their
leaves
CondensationWater vapor condenses as clouds
PrecipitationMoisture released by clouds (clouds are droplets of
water).Rain, snow, sleet and hail
What percentage of the Earths water is fresh water available for
use by living organisms?DISTRIBUTION Of WATER70.9% of the Earths
surface is covered by water.Oceans hold 97% of surface
water.Glaciers and polar ice caps hold 2.4%Rivers, lakes, ponds and
groundwater holds contains the remaining 0.6%A very small amount of
the Earths water is contained within biological bodies and
manufactured products.Water PurificationWater purification is the
process of removing undesirable chemicals, materials, and
biological contaminants from contaminated water.
Why do we purify water?Human consumption drinking waterMedical
applicationsPharmacological applicationsChemical
applicationsIndustrial applicationsMethods of Water
Purificationphysical processes such as filtration and
sedimentationbiological processes such as slow sand filters or
activated sludge chemical processes such as flocculation and
chlorination the use of electromagnetic radiation such as
ultraviolet light.Purification of Drinking WaterThe United States
has nearly 60,000 municipal water facilities that serve 232 million
people. Surface water sources of municipal water supplies include
streams, rivers and lakes.Often a dam is built across a river or
stream to form an artificial lake or reservoir. Reservoirs
accumulate water when there is an adequate supply and store it for
use during periods of drought.Water PurificationIn the United
States most municipal water supplies are treated before being used
so that the water is safe to drink. Turbid water is treated with a
chemical coagulant that causes the suspended particles to clump
together and settle out (flocculation and sedimentation). The water
is then filtered through sand to remove remaining suspended
materials as well as many microorganisms. Water PurificationIn the
final purification the water is disinfected to kill any remaining
disease causing agents. The most common way to disinfect water is
to add chlorine.Other types of disinfection systems use ozone or
ultraviolet(UV) radiation. Water Purification TechniquesPhysical
(Filtering, settling)Biological (Bacteria eat or organic matter in
water)Chemical (Removal of chemicals and kill of
pathogens)Distillation (boiling)Reverse osmosis (Filters so small
they can block individual molecules larger than water)What is
distillation?Water is boiled and turned into a gas (water vapor.)
The water vapor travels down a long tube where it is cooled. The
water vapor then condenses back into liquid and is stored in a
containerDistallation removes nearly all impurities from the water
because nothing else boils at the same temperature.Distallation is
expensive because it takes a lot of energy to boil water. This is
too expensive for largeMunicipal water treatment facilities. How
has human activity negatively impacted the worlds water supply?
Waste SpillsHuman wasteHazardous wasteLandfill wasteRadioactive
waste