Exam #1 Study Guide
• 14.1 Water: Some Unique Properties
o Solid form of water (ice) is less dense than the liquid. This means water
expands when it freezes.
Ice insulates the lower layers of water; this allows fish and other
aquatic animals to survive winter in the temperate zones.
Water is also denser than most other liquids ▯therefore liquids that
don’t dissolve in water float to the top.
o Water has a high specific heat. Specific heat is the quantity of heat
required to raise the temperature of 1 g of a substance by 1 °C.
o Water also has a high heat of vaporization ▯a large amount of heat is
required to evaporate a small amount of water.
o Water is a highly polar molecule
Liquid state – molecules are tumbling over one another but
remain associated through strong hydrogen bonds.
Gaseous state – molecules tumbling so violently that they break
all of the hydrogen bonds and bond with molecules surrounding
Solid state – molecules take on a more ordered arrangement
forming 4 hydrogen bonds per molecule. Solid ice contains large
hexagonal holes, which extend out for billions and billions of
• 14.2 Water in Nature
o ¾ of the Earth’s surface is covered in water, 98% of which is seawater.
Less than 1% of all Earth’s water is available for human
consumption ▯lakes and streams account for 0.01%.
Because water is a polar solvent, it readily dissolves most ionic
substances ▯sun heats part of water and leaves salts behind.
875 million people have inadequate quantities of fresh water.
o The Water Cycle and Natural Contamination
Rainwater picks up dust particles, oxygen, nitrogen and carbon
Carbon dioxide makes rainwater acidic because it reacts with water
to make carbonic acid (H 2CO 3).
Groundwater also contains small amounts of radon o Dissolved Minerals
Hard Water – Calcium (Ca2+), Magnesium (Mg2+), or iron salts
Soft Water – Sodium (Na+) and Potassium (K+)
o Organic Matter
Rainwater dissolves matter from decaying plants and animals ▯this
can enrich the soil but in large quantities it can contaminate water.
Bacteria, lubricants, fuels, fertilizers, microorganisms, and
pesticides are all potential contaminants of natural waters.
• 14.3 Chemical and Biological Contamination
o Pathogenic microorganisms (prokaryote) – disease causing organisms
from human wastes
Cholera, typhoid fever, dysentery, cryptosporidium, and giardia.
o Pathogenic protozoa (eukaryote) – from animal and human feces
o 30 million people in US are still threatened by pathogenic
80% of all illnesses in the world is caused by water contamination.
• Acid Waters o Acids formed from sulfur oxides (SOx) and nitrogen oxides (NOx) come
down from the sky in acid rain, fog and snow ▯corrode metals, dissolve
limestone and marble.
o Acids flow into streams and lakes from abandoned mines ▯detrimental to
Very acidic lakes are often clear and sparkling.
• Sewage and Dying Lakes
o The breakdown of organic matter by bacteria depletes dissolved oxygen
(DO) in the water and increases the plant nutrients in water.
o Aerobic oxidation (degradation) – biodegradation that occurs in the
presence of dissolved oxygen
o Biochemical oxygen demand (BOD) – is a measure of the amount of
oxygen needed for aerobic degradation to occur.
The greater the quantity of degradable organic wastes, the higher
the BOD. If the BOD in a lake or stream is high enough, dissolved
oxygen is depleted and no life can survive.
o Nitrates and phosphates may serve as nutrients for the growth of algae,
which can cause problems.
o Eutrophication – when the algae die, they become organic waste and
increase the BOD of the water.
This process can be accelerated by human waste, phosphates from
detergents, and fertilizers.
o Anaerobic decay – when too much organic matter depletes the DO in a
body of water this process takes over (without oxygen). Anaerobic decay
reduces organic matter instead of oxidizing it. • Green Chemistry
o Zeolites – are a class of solids that both occur naturally and can be
They are minerals that have a framework made of silicon,
aluminum and oxygen.
The open structure of zeolites allows them to be used in a variety
of waterremediation applications.
They help reduce the amount of waste in water but do not become
part of the waste that is generated.
• 14.4 Water: Who uses it and how much?
o About 70% of the world’ freshwater supply is used in agriculture, almost
all of it for irrigation. Another majority of water is used for cooling
electric power plants.
o Much of the water used in the production of industrial and consumer
products is cleaned up and recycled.
o In the US, every person uses 7 L for dinking and cooking purposes but
directly uses a total of about 380 L.
o Automobile Manufacturing
Cyanide (CN) and chromate (CrO 4) both toxic are products of
chrome plating processes ▯chemical engineers have implemented
chemical processes that convert the molecules above to relatively
• 14. 5 Groundwater Contamination ▯Tainted Tap Water
Well water is sometimes contaminated with nitrate ions (NO 3)
• Excess nitrates can be dangerous to infants ▯Nitrate to
nitrite ions ▯methemoglobinemia, blue baby syndrome
• Nitrates in groundwater comes from fertilizers
o Volatile Organic Chemicals (VOCs)
Something that is volatile evaporates easily without excessive
VOCs are also air pollutants and can contaminate groundwater and
add undesirable odors to drinking water.
VOCs include trichloroethylene (drycleaning solvent) and come
from industrial activity, landfills, and gasoline leaks etc…
o Leaking underground storage tanks
Contaminate groundwater from petroleum, lead, mercury and other
• 14.6 Making Water Fit to Drink
o Safe Drinking Water Act Passed in 1974 by EPA to set, monitor and enforce national health
based standards for a variety of contaminants in municipal water
• 90 regulated substances under this act.
o But Not a Drop to Drink
Clean drinking water is scarce in Bangladesh ▯40 years ago
thousands of tubewells were constructed to provide clean drinking
water within 100m of every family ▯halved infant mortality rate.
Now chronic arsenic poisoning is a new risk ▯arsenic occurs
naturally in the mineral formations of the region.
Arsenic threatens over 100 million people in Bangladesh ▯ deeper
wells and certain types of charcoal/ceramic filters can get rid of
arsenic but most people can’t afford this.
o Water Treatment
The first step in water treatment is to add slaked lime and alum (a
flocculent – a substance that causes particles to clump
• The aluminum hydroxide coagulates colloidal particles and
bacteria. These are then removed by filtering through sand
and gravel filters.
• It is then aerated to improve tasted and remove odors.
o Chemical Disinfection
Chlorine (Cl 2)– is added to kill any remaining bacteria.
• Risk of chlorine treatment – harmful chlorinated
compounds can form