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WATERHOLICA DROP OF WATER – A DROP OF HOPE

SCIENTIFIC FACTS ON WATER

CHEMISTRY

ESPERINO GENIKO LYKEIO LAMIAS

A colorless, odorless, tasteless liquid, water is the only common substance that occurs naturally on the earth in all three states : solid, liquid and gas.

Approximately 73% the earth’s surface, almost 328 million cubic miles, is covered with water.

The human body is 70% water by weight and water is essential to the life of every living thing.

THE WATER MOLECULE STRUCTURE Water is the most abundant molecule on Earth’s surface. It’s a

chemical compound with the chemical formula H2O and consists of two atoms of hydrogen bonded to one atom of oxygen. The bonds which hold the hydrogen and oxygen atoms together are called covalent bonds. The water molecule forms an angle (104.3 degrees),with hydrogen atoms at the tips and oxygen at the vertex.

An important feature of water is its polar nature. The side with the hydrogen atoms which has a positive charge attracts the oxygen side which has a negative charge. This charge difference is called a dipole. Since opposite electrical charges attract each other these charge differences cause water molecules to be attracted to each other and to other polar molecules. This attraction contributes to hydrogen bonding and explains many of the amazing properties of water.

Water is called universal solvent because it is capable of dissolving a variety of different substances, in fact more substances than any other liquid. This is important to every living thing on Earth. It means that wherever water goes either through the air, ground or our bodies it takes along chemicals, minerals and nutrients.

Cohesion when water molecules are attracted to water molecules and adhesion when water molecules are attracted to molecules of other substances.

UNIQUE PROPERTIES OF WATER

High surface tension shows that water is sticky and elastic and tends to clump together in drops rather than spread out. Surface tension is responsible for capillary action.

High heat capacity means that it can absorb a lot of heat before it begins to get hot.

Changes in density based on temperature. Water freezes at 00

C and boils at 1000 C. The solid form of water, ice is less dense than the liquid form which is why ice floats.

PH is the value that determines if water is acidic, neutral or basic. It is measured on a scale from 0 to 14 on which 7 means water is neutral. PH values less than 7 indicate that water is acidic and pH values more than 7 indicate that it is basic. It is a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Since pH can be affected by chemicals in the water it is an important indicator of water that is changing chemically. Water with a pH of 5 is ten times more acidic than water having a pH of 6. Pollution can change water’s pH, which in turn can harm animals and plants living in the water. Pure water is neither acidic nor basic.

WATER QUALITY PROPERTIES

Turbidity is a measure of non - transparency of water due to the presence of suspended materials that scatter light passing through the water.

Conductivity is the ability of water to conduct electrical current. It is dependent on the amount of dissolved solids. Distilled water has lower conductivity than sea water.

Alkalinity is the amount of buffering material in the water to neutralise an acid or a base , so that the pH of the water will not change.

Hardness indicates the excessive amount of dissolved minerals, such as calcium and magnesium in water.

Dissolved oxygen is a measure of how much oxygen is dissolved in water. Although water molecules contain an oxygen atom, this oxygen is not what is needed by aquatic organisms to breathe and survive.

Water temperature affects the feeding, reproduction and metabolism of aquatic species. Temperature also can affect dissolved oxygen levels as well as the ability of organisms to resist certain pollutants.

Water color blue :transparent water with a low accumulation of dissolved materials, yellow or brown: dissolved organic materials, humic substances from soil ,peat or decaying plant material, red: can be produced by some algae, green: water rich in phytoplangton and other algae, a variety of yellow, red, brown and grey colors: may be caused by soil runoff.

Odor sewage and industrial waste or decomposing vegetation and microbial activity can cause odor although water is odorless.

Suspended sediment is the amount of soil in water. During rain storms, soil is washed away and the amount depends on the type of land and the vegetation surrounding the water. Excess sediment can harm the water quality.

Nitrates - Nitrogen are essential for plant growth but excessive amounts in water supplies presents a major pollution problem. They may enter water from agricultural fertilizers, human sewage, industrial wastes, livestock wastes and farm manure.

Phosphates are applied as fertilizer to agricultural fields, grass lawns and golf courses. Phosphates can accelerate the growth of algae and aquatic plants and therefore cause eutrophication.

Carbon Dioxide in water is necessary for aquatic organism growth and respiration. CO2 increases when organic wastes reduce the oxygen available for these organisms.

Iron in water may stain fixtures and may have an odor or taste. High values in water may indicate contamination from land fills

Fresh water is water which occurs on Earth’s surface (lakes, streams, rivers) and underground, containing minimal quantities of dissolved salts.

Bottled water is drinking water packaged in plastic or glass bottles and it can be carbonated or not.

Mineral water comes from mineral springs and contains amounts of dissolved minerals and salts (calcium, sodium, magnesium, iron) and sulfur compounds.

Carbonated water is water in which carbon dioxide gas under pressure has been dissolved. It is the major ingredient of carbonated soft drinks.

Purified water is mechanically filtered and processed to be cleaned for usage. Most common forms are distilled and deionized water used in science, industries and engineering labs.

MORE WATER

Hard water is water with large concentrations of alkaline salts such as calcium and magnesium.

Soft water does not contain large concentrations of calcium and magnesium.

Heavy water is water in which both H atoms have been replaced with deuterium , the isotope of hydrogen containing one proton and one neutron.

Brackish water is mixed fresh and salt water due to salt water intrusion into coastal water wells.

Saline water or salt water contains significant amounts of dissolved salts, most common of all sodium chlorine (NaCl). Desalination is the removal of salts from saline water to produce fresh water.

Water pollution is the contamination of water bodies such as lakes, rivers, oceans and groundwater caused by activities of people and can be harmful to organisms and plants which live in the water and human beings as well.

The water pollutants can be organic and inorganic.

WATER POLLUTION

Detergents Disinfection by-products found in chemical disinfected

drinking water such as chloroform Food processing waste which include oxygen demanding

substances, fats and grease Insecticides, herbicides, a huge range of organohalides and

other chemical compounds Petroleum hydrocarbons, including fuels, lubricants and fuel

combustion by products from stormwater runoff

ORGANIC WATER POLLUTANTS INCLUDE

Tree and bush debris from logging operations Volatile organic compounds (VOCs) such as industrial solvents

from improper use Chlorinated solvents which are dense non-aqueous phase

liquids (DNAPLs) Various chemical compounds found in personal hygiene and

cosmetic products Drug pollution involving pharmaceutical drugs and their

metabolites.

Acidity caused by industrial discharges (especially sulfur dioxide from power plants)

Ammonia from food processing waste Chemical waste as industrial by-products Fertilizers containing nutrients, nitrates and phosphates,

which are found in stormwater runoff from agriculture as well as commercial and residential use

Heavy metals from motors vehicles and acid mine drainage Silt runoff from construction sites, logging, slash and burn

techniques or land cleaning sites.

INORGANIC WATER POLLUTANTS INCLUDE

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