WATER

CONTENT
⦁ Definition of Water
⦁ Sources of Water
⦁ Treated Water
⦁ Distilled Water
⦁ Types of Water (Soft and Hard)
⦁ Water Pollutants
⦁ Properties of Water
⦁ Uses of Water
⦁ Laboratory Preparation of Water

Definition of Water
“Water is Life”. It is the most important and the most abundant on earth. It is of great importance to all plants and animals. The human body is over 6o percent water and it is present in equally the same amount in plants. It should however be noted that water is not available everywhere and its availability at certain parts of the world has led to the influx of man to those areas to set up villages and towns.
Sources of Water
Water can either be found as a natural source or as treated water. There are many sources of water found on the earth’s surface, they include rain water, spring water, well-water, river water, lake water and sea-water. Rain water is the purest form of natural water because it is formed as a result condensation of water in the atmosphere. Spring water contains a considerable amount of mineral salt; but very little suspended impurities such as dust and bacteria. Well-water contains a lot or clay and other mineral salts. Deep well-water tends to be less polluted than surface well-water. River water, Lake water and Sea-water contain a lot of dissolved air, mineral salts, bacteria and organic remains.
All these waters have to be purified before they can be used for drinking. And all the type of natural water are in constant circulation, forming a gigantic water cycle.
Treated Water
Treated water are usually prepared for special purposes. Examples are distilled water, pipe-borne water for townships and chlorinated water used in swimming pool.
Distilled Water
Distilled water is chemically pure water prepared by condensing steam using Liebig condenser. If ion exchange resin is used in preparing the water, it is called ionized water.
EVALUATION
⦁ (a) List four sources of water. (b) Which of the listed source of water in (a) is the purest? Give reason.
⦁ Explain the how distilled water is obtained.

Types of Water (Soft and Hard)
Water is of two types namely: Soft water and Hard water.
(i) Soft water:
Water is said to be soft if it readily forms lather with soap. Examples are rain water, tap water.
(ii) Hard water:
Hard water is water which will not form lather with soap. Examples are river water, lake water, stream water and sea water.
Types of Hard Water
There are two types of hard water namely:
⦁ Temporary hard water: This the hardness caused by the presence of dissolved Ca(HCO3) and MgCO3 in water and can be removed by boiling.
⦁ Permanent hardness: This is the hardness caused by the presence of CaSO4, MgSO4 and chlorides which cannot be removed by boiling but by addition of washing soda, caustic soda and ion exchange method.
Advantages of Hard Water
⦁ It has pleasant taste than soft water and tasteless water.
⦁ It does not dissolve lead pipes of pots unlike soft water which dissolves led pipes.
⦁ It is good for healthy teeth and bones because it contains calcium which is an important element in formation of teeth and bones of animals.
⦁ Animals like snail and crabs are able to make their shell with the help of hard water.
Disadvantages of Hard Water
⦁ It causes furring of kettle and boilers unlike soft water.
⦁ It infers with processes used to dye materials and tan hides.
⦁ It forms scum with soap thus, wasting soap unlike soft water.
EVALUATION
⦁ What are the natural sources of water
⦁ Differentiate between soft water and hard water
⦁ Mention three (3) advantages and two (2) disadvantages of hard water

Water Pollutants
The common pollutants are as follows:
(a) Crude oil spills:
Accidents and carelessness in oil rigs and tankers cause oil spills mainly in the coaster waters. The oil floats on water and kills most of the marine life in the affected areas. The oil is then washed up on the beach, temporarily preventing people from using the water for recreation.
(b) Industrial and agricultural wastes:
Chemical wastes from industries and agriculture;  such as acids, organic solvents, mercury compounds, fertilizers, insecticides, etc that are emptied directly into rivers untreated causes water pollution and endangers aquatic life. For instance, mercury compounds accumulate in the body of the aquatic organism like fish and this eventually causes food poison in the animal that feeds on such fish.
(c) Refuge and sewage:
It is common practice to see people dump refuse and human wastes into a nearby river. Most of these refuge and sewage are pollutants which are biodegradable i.e. they can decomposed by decomposers such as bacteria which uses up the oxygen present in the water.
EVALUATION
⦁ Mention two sources of water pollution.
⦁ Briefly discuss how polluted water can be treated.
Properties of Water
Physical Properties of Water
⦁ Pure water is colourless, odourless and tasteless.
⦁ It is a liquid at room temperature.
⦁ It boils at 100oC and freezes at 0oC.
⦁ It has a density of 1 gcm-3 at 4oc.
⦁ It is neutral to litmus.
Chemical Properties of Water
⦁ Water reacts with metals such as sodium, potassium, calcium etc forming alkalis with the liberation of hydrogen gas.
⦁ Water reacts with non-metals e.g carbon with the liberation of carbon (II) oxide and hydrogen gas.
⦁ Water reacts with sodium oxide and potassium oxide with the formation of strong alkalis such as sodium hydroxide and potassium hydroxide.
Uses of Water
⦁ Water is used for cooking and drinking.
⦁ It is used as a means of transport.
⦁ It is used in the manufacturing of drugs.
⦁ It is also used in car batteries
⦁ It is used in the laboratory for preparing reagents and for carrying out analysis.
Laboratory Preparation of Water
Water is prepared from its constituent elements, i.e. hydrogen and oxygen. Hydrogen is generated by the action of fairly concentrated hydrochloric acid on zinc. The gas then passed through a U-tube containing anhydrous calcium chloride gas, the hydrogen is burnt at a jet and the vapours are ‘cooled’ when they come in contact with a clean can kept cool by water. A test tube is placed over the jet to collect hydrogen gas by displacement of air. When the test tube is full of gas, it burns on the application of to it, light the jet and allow the flame to burn very close to the can. Moisture will condense on the can and will drop into a dish which is placed below the liquid.
The liquid can be shown as water using:
⦁ Action of the liquid on anhydrous copper (II) tetraoxosulphate (VI) and cobalt (II) chloride salt.
⦁ Boiling point of the water.
EVALUATION
⦁ What are the pollutants that can be present in water
⦁ (a) Give four uses of water. (b) How can water be prepared in the laboratory?
⦁ Distinguish distilled water from treated water.
⦁ (a) Mention two types of hardness of water (b) List two salts that cause each of them.
⦁ Describe an experiment to show that contains hydrogen and oxygen only.
⦁ What term is used to describe water sample that: (a) produces lather with soap (b) does not produce lather with soap.
⦁ State two advantages of soft water over hard water. (b) List two advantages of hard water.
⦁ Enumerate three water pollutants you know