Teaching Environmental Studies Water Notes - Water

 

Water

 

Water occupies a very large area of the Earth's surface, it is renewable resource which is essential for sustenance of life. Most of the water on Earth's surface is found in seas and oceans is saline in nature. Fresh water is found frozen in the ice-caps at the two poles and on snow covered mountains. The underground water and water in rivers, lakes and ponds is also fresh.

 

6.1 Sources of Water

 

Earth is called as 'blue planet' because of abundance of water of Earth. About 71% of Earth's surface is covered by water, which produce a blue colour reflection when viewed from space.

97.5% of Earth's water is present in oceans. Water also exists in air as water vapour, in rivers and lakes, in icecaps and glaciers. Only 2.5% water present on Earth is fresh water,

 

Percentage of Water on Earth

                       

Sources	Percentage
Oceans	97.2
Sea and salty lakes	0.008
Glaciers and polar ice	2.15
Underground water	0.625
Rivers arid sweet water lakes	0.0091
Atmosphere	0.001
Other sources	0.0069
Total water	100

 

6.2.1 Properties of Water

Water is a compound made up of hydrogen and oxygen and it exists in three stages: solid (ice); liquid (water) and gas (water vapour).

These-three stages of water are inter changeable.

 

·      Pure water is transparent, colourless, odourless and tasteless. Water takes up the colour, odour and taste of the substance that dissolves in it.

·      Water has no definite shape, it takes the shape of the vessels in which it is stored.

·      Water allows the light to pass through it, this helps the marine animals to find their prey 2nd protect themselves from their enemies. The temperature at which a liquid boils and tons to vapour is called its boiling point \[(212{}^\circ F)\,100{}^\circ C\]  is the boiling point of water.

·      By heating water evaporates and converted into gaseous form. Evaporation of water takes

Pace at all temperature, but rate of evaporation is highest at boiling point.

For boiling external energy source i.e. extra heat is required while evaporation does not need external source of energy. Atmospheric heat is sufficient for evaporation. In summers, wet clothes dries easily as water is lost from cloths due to evaporation.

The temperature at which a liquid changes into solid is called its freezing point. \[0{}^\circ \text{ (}32{}^\circ F)\] is the freezing point of water.

·         Condensation is the process of conversion of a vapours or gas to liquid. Clouds are formed by condensation in the air.

·         At \[4{}^\circ C,\] water has the least volume and maximum density (heaviest). This property of water plays an important role in survival of aquatic life in polar region, where only .upper layer of lakes and river gets frozen.

·         Things that have density more than water will sink in water and things that have lesser density than water will float on the water. e.g. wooden boat, iron ship, empty plastic bottle, empty bowl, ice and soap with soap case will float in water. Whereas bowl filled with pebbles, iron, nail, needle, spoon, bottle full of water, soap cake etc will sink in a water.

·         Lemon and egg when placed in pure water will sink in water, but when same lemon and egg are placed in water in which good amount of salt is present will float in water. This phenomenon can be explained by density, but in simple words it can be understood as the thing which will be heavier than water will sink and thing which will be lighter will float on the water surface.

 

6.1.2 Uses of Water

·         Our human body is made up of 70% of water.

Water is the main constituent of our cell, tissue blood and it plays very important role in metabolic activities of the body.

 

·         Water is essential for the germination of seeds and growth of plants. Water is consumed by the plant during process of photosynthesis plants break water to provide oxygen.

·         Water helps in transportation of nutrient and mineral in plants.

·         Water plays a variety of roles in*our body like, helps in digestion of food, it facilitates the absorption of nutrients in the blood and then their distribution to various body parts.

·         Water helps in maintaining body temperature by sweating. In this process, a part of energy taken away from the body as sweat.

·         Water take dissolved nutrients and oxygen from water for survival. In aquarium, if one use boiled or distilled water fishes are not able to survive due to absence of minerals.

·         A pore on the top surface of aquarium or a air pump is used to pump oxygen in aquarium.

 

6.1.3 Types of Water

Water can be categorised in various types. These are as follow

 

Heavy Water \[({{D}_{2}}O)\]

Heavy water was discovered by Harold Urey in 1931, according to him only one part of 6000 part of normal water is heavy water. Heavy water is obtained by the electrolysis of normal water. Its atomic weight is 20 gram/mole.   

Heavy water is not radioactive. \[{{D}_{2}}O\] is harmful for organisms.

 

Uses of Heavy Water

Being harmful heavy water is useful also in many ways.

These are

·         \[{{D}_{2}}O\] is used in nuclear reactors, as neutron moderator to slow down neutrons.

·         To produce deuterium.

·         It is used as a tracer compound to study the mechanism of chemical reaction and in biochemical reactions.

 

Hard Water and Soft Water

The water which produce large amount of lather with soap is known as soft water while hard water which form scum with soap is known as hard water.

 

Hardness of water can be of two types i.e.

·         Permanent Hardness It is due to the presence of sulphates and chlorides of magnesium and calcium.

·         Temporary Hardness Bicarbonates of calcium and magnesium is the cause of temporary hardness.

 

Removal of Hardness

Hardness of water can be removed by using different methods. These are as follow

·         By boiling water soluble bicarbonates are converted into insoluble carbonates, which will settle down and can be removed by filtering the water.

·         By adding lime water bicarbonates of magnesium and calcium react with lime water and precipitates of calcium carbonates and magnesium carbonates are formed and get settled down.

 

Potable Water

·         The water suitable for drinking is called potable water.

·         Water we get from various sources may not be fit for drinking, it can have dissolved salts, suspended particles and microorganisms. Some minerals dissolved in water are essential for our body, but if they exceed in amount then they need to removed. Microorganisms should be killed before the supply.

·         Bleaching powder is added to kill harmful bacteria present in water.

·         Potassium permagenate is used to clean water of well.

·         It is advisable to boil water before drinking most of the microorganisms are killed at \[100{}^\circ \text{ }C\].

·         Porcelain candle water filter, UV water filter are used now-a-days for water filteration.

 

How Salt is made from Sea Water?

The sea water is collected in shallow beds dug in the sand. Water is allowed to dry in the Sun and after the water dried salts remained on the ground.

During movement for Independence, Gandhiji went on Dandi March to make a salt at the sea coast.

During that time, law did not allowed Indian people to make salt themselves and law also put heavy taxation on salt. In order to protest against this law, 

 

Gandhiji went on Dandi March in year 1930.

 

Dead Sea

All ocean and sea have salty water. The saltiest of all S is the dead sea" Approximately 300 grams of salt is present in one litre of water. Even if a person who does not know how to swim will not drown in this sea, person will float as if lying down on it.

 

6.1.4 Pollution of Water

 

Water often get mixed with unwanted materials and living organisms. Such water is called polluted water. It is not fit for drinking and bathing.

 

Main causes of water pollution are as follow

·         Industrial waste

·         Sewage and waste water Mining activities

·         Marine dumping

·         Accidental oil leakage

·         Burning of fossil fuels

·         Chemical fertiliser and pesticides & Leakage from sewer lives

·         Global warming

·         Radioactive waste

·         Urban development

·         Leakage from the landfills

·         Underground storage leakage of coal, petroleum product through underground pipes

·         Due to acid rain, in which acidic compounds like nitric acid \[(HN{{O}_{3}})\] and sulphuric acid \[({{H}_{2}}S{{O}_{4}})\] is present

 

·         Biological Oxygen Demand (BOD) Pollution level of water can be determine by BOD. It is a measurement of the amount of Dissolved Oxygen (DO) that is used by aerobic microorganisms when decomposing organic matter present in water. It i's most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days (BODs) of incubation at\[20{}^\circ C\].   

 

Solution for Water Pollution

 

Polluted water can be treated by using different methods and by making people aware.

Water pollution can be prevented by following steps

·         Sewage should be treated properly human and animal excreta should be prevented from mixing with water resources. It can be used in biogas plant for clean fuel and fertilizer.

·         Polluted river do not have ability to clean easily by natural process, so people should not allow to throw waste into river.

·         There should be some laws and legislation for effluent flow from factories. Factories should have necessarily a water treatment plant where toxic chemicals must be treated and converted into harmless substances.

·         People should made aware about the harms of water pollutions.   

 

6.1.5 Underground Water

 

Water present in the cracks and space in soil, sand and rock beneath Earth surface. Underground water almost found everywhere. The water table may be deep or shallow of a particular place. Heavy rains or melting of snow may increase underground water level while heavy pumping of groundwater supplies may cause the water table decrease.

Groundwater is now a days critically polluted by many human activities. A groundwater pollutant is any substance that, when it reaches an aquifer, make water unsuitable for use. If heavy metals enter the groundwater they cannot be removed. They can be diluted, but they forever stuck to aquifers. The pollution of groundwater by arsenic and fluoride has been identified in many developing and developed nations.

 

·         Minamata is a neurological syndrome, caused by. severe mercury poisoning through water, it effect on central nervous system. The most common source is seafood contamination.

·         Radioactive elements present in environment increase the risk of damage of vital molecules.

·         Cells and tissues may also cause many genetic disorders, cancers, birth defects etc.

 

6.1.6 Conservation of Water

 

Only a very few percentage of water available is fit for use. With the increase of population demand of water is increasing day-by-day. So, we have to conserve water. Rain water harvesting is used for this purpose.

Rainwater Harvesting

One way of increasing the availability of water is to collect rainwater and store it for later use. "Catch water where it falls" is the basic idea of rainwater harvesting.

Rain water harvesting can be done with the help of following techniques

·         Rainwater is collected from rooftop to a storage tank through pipes in this system. Water should be filtered first before use because it contains soil.

·         Rainwater should allow to go into ground directly from roadside drains.

 

Institutions Related to Water

 

Conservation

Institution related to water conservation water is most precious gift of nature to us, so to preserve water for present and future use many programmes, institutions and NGO's are join together, 22nd March' is celebrated as 'World Water Day'.

 

·         Tarun Bharat Sangh 'Jal Punish' (Water man)

Rajendra Singh is related with this institute. This institute related to Rajasthan.

·         Bheem Sangh This is related with Holkundi, Karnataka.

·         Sparsh Ganga Abhiyan Main aim of this movement is to clean 'Ganga'. This movement is related with 'Uttarakhand'.

·         Pani Panchayat In 1972, Maharashtra Pani Panchayat was started for the conservation of water.

 

6.1.7 Waterborne Diseases

 

Many diseases spread through consumption of impure water. Few of the diseases which are spread by water are : hepatitis, diarrhoea, stomach infection, typhoid, malaria, dengue, chikungunya, cholera, jaundice etc water borne diseases are caused by pathogenic microorganism that are transmitted through contaminated water.

·            Infection can result by consuming infected water.

Washing and bathing in infected water can damage skin and cause allergy.

·            Water provides the breeding place mosquitoes and these mosquitoes can cause malaria, dengue and chikungunya.

·            Treating the water is only effective way of controlling diseases like hepatitis, jaundice, diarrhoea etc and preventing the breeding of mosquitoes is important in controlling diseases like malaria, chikungunya and dengue.

·            Breeding takes place in clean water, so in order to prevent breeding of mosquitoes

·            do not allow water to collect around house.

·            do not keep stagnant water for long time in any water pots, cooler, tanks etc covered the stored water and clean them regularly.

·            Kerosene should be added in the collected water as kerosene will spread on top of water surface and it will not allow mosquitoes to .breed.

Mosquito net should be used to prevent the mosquitoes bite.

 

Point to be Remember

·         India is first in tubewell irrigation.

·         Olive ridley turtles found mostly in Indian Ocean and Pacific Ocean. Among other turtle species these are maximum in Indian Ocean.

·         Hydrophilic salt attracted to water molecule while hydrophobic salt never react with water.

·         Silver iodide is used for artificial rain.

 

Malaria

The disease is found in area where lot of rain and humidity is. Scientists named Ronald Ross discovered that Malaria is caused by mosquito and he was awarded Nobel prize for his work in 1905.

He found the kind of mosquito that was actually responsible for causing Malaria. He concluded that the female Anopheles mosquitoes spread the disease.

·         This disease is characterised by high fever with shivering and followed by sweating. For detection of disease, blood testing is done, parasite is present in RBC and then medicines are prescribed for remedy. From early times, the dried and powdered bark of cinchona tree was used to make a medicine for malaria. Earlier people used to boil the bark powder and strain the water which was given to patients. Now tablets made from cinchona are used as medicines.