Chapter 5(II) - Water and Solution

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WATER AND SOLUTIONFORM 2

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Water is a ubiquitous chemicalsubstance, composed ofhydrogenand oxygen, that is essential for thesurvival of all known forms oflife.

In typical usage, water refers only toits liquid form or state, but thesubstance also has a solid state, ice,

and a gaseous state, water vapor orsteam.

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The five most commonly considered physical

characteristics are temperature, taste, colour, odour andturbidity.

Water is a tasteless, odorless liquid at standard

temperature and pressure.

The color of water and ice is, intrinsically, a very light

blue hue, although water appears colorless in small

quantities.

Ice also appears colorless, and water vapor is

essentially invisible as a gas.

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The freezing point of water is 0 Celsius or

32

Fahrenheit.

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Water boils at 100 degrees Celsius or 212 degrees

Fahrenheit under standard conditions at sea level

(at one atmosphere of pressure).

The boiling point of water and any other

substance depends on the atmospheric pressure,

which changes with elevation. At higheraltitudes, the pressure is lower, and so water

boils at a lower temperature. If the barometric

pressure is not at the standard value, the boilingpoint will be different.

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Contaminants in raw water

The unique ability of water to dissolve, to some

extent, virtually every chemical compound and

support practically every form of life means that

raw water supplies contain many contaminants.

The major categories of impurities found in raw

water include:Suspended particles, including colloids

Dissolved inorganic salts

Dissolved organic compounds

Micro-organisms

Pyrogens

Dissolved gases

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Electrolysis of water is the decomposition ofwater (H2O)

into oxygen (O2) and hydrogen gas (H2) due to an electric

current being passed through the water.

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solution is a homogeneousmixture

composed of two or more substances

solute is dissolved in another substance,

known as a solvent.

solvent is a liquid or gas that dissolves a

solid, liquid, or gaseous solute, resulting in

a solution.

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Concentrated solutionIt refers to a solution in which much of the water has

been removed.

Dilute solutionto make (a liquid) thinner or weaker by the addition of

water or the like.

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Saturated solution

solution in which the maximum amount of solvent has been

dissolved. Any more solute added will sit as crystals on the bottom

of the container.

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ACIDSTaste: Sour.

Touch: Like water.

Tested with litmus paper: Turn blue litmus red.pH value: From 0 to less than 7.

Reaction with metals: Form hydrogen and a salt.

Reaction with carbonates: Form a salt, water and carbon dioxide.

Reaction with ammonium compounds: No reaction.

ALKALISTaste: Bitter.

Touch: Soapy.

Tested with litmus paper: Turn red litmus blue.

pH value: From above 7 to 14.

Reaction with metals: No reaction.

Reaction with carbonates: No reaction.

Reaction with ammonium compounds: Give off ammonia gas

NEUTRAL

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a chemical reaction

(also called a water forming reaction since a water

molecule is formed during the process)

in which an acid and a base or alkali (soluble base)

react to produce salt and water (H2O).

NEUTRALISATION

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WATER PURIFICATION

is the process of removing undesirable chemicals, materials,and biological contaminants from raw water.

The goal is to produce water fit for a specific purpose. Most

water is purified for human consumption (drinking water) but

water purification may also be designed for a variety of other

purposes, including to meet the requirements of medical,

pharmacology, chemical and industrial applications.

In general the methods used include

physical process such as filtration and sedimentation

biological processes such as slow sand filters or activatedsludge

chemical process such as flocculation and chlorination and the

use of electromagnetic radiation such as ultraviolet light.

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WATER SUPPLY

Is the process of self-provision or provision bythird parties in the water industry, commonly a

public utility, ofwater resources of various

qualities to different users. Irrigation is covered

separately.

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Here are some ways to save water.

Install a water meterCheck your plumbing for leaks, especially leaking

toilets and faucets.

Take shorter showers.

Catch the cold water that comes out of the faucet,

tap, or shower while you are waiting for the hot

water.

turn the faucet/tap offwhile you are brushing yourteeth, shaving, washing your hands, doing dishes,

and so on.

Catch the rain. Use it for watering your plants, lawn

or garden.

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