Value Based Questions in Science for Class 9 Chapter 14 Natural Resources
These Solutions are part of Value Based Questions in Science for Class 9. Here we have given Value Based Questions in Science for Class 9 Chapter 14 Natural Resources
It has been made mandatory to install rain water harvesting system and solar water heater in all buildings in urban areas,
- What is the rationale when rain water already passes into drains ?
- Why are solar water heaters being installed when electric geijers are available ?
- Rain water passed into drain does not enter the ground but is taken out of the urban area and poured into a water body at quite a distance with or without treatment. However, ground water is being withdrawn everywhere for drinking, industrial and irrigation purposes. As a result, the level of ground water is going down and arid conditions are being faced in many areas. In rain water harvesting, rain water from a building is passed directly into ground, dug wells or water pumps. This recharges ground water.
- Installation of solar water heaters is a method of saving electricity which is always in short supply due to rapid urbanisation, Industrialisation and intensive agriculture. Coal/gas based power plants are adding CO2 to the atmosphere causing global warming. Saving electricity is now an important social responsibility.
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- Sheela saw blue-green algae forming bloom in the village pond,
- Fish, which was previously abundant was no-where to be seen.
- The pond is giving a stink. Water of the pond is not even fit for cattle. Some of the cattle who were taken to the pond for drinking and bathing have fallen sick,
- What explanation will Sheela give for this to the villagers.
- Bloom forming algae occur in a pond only when the quality of pond water has deteriorated due to pollution. Blue-green algae secrete toxins that are harmful to animals and humans,
- Fish must have died due to deficiency of oxygen in pond water. Oxygen deficiency occurs when there is excess of organic matter (organic loading). The aerobic decomposers consume the dissolved oxygen. This is followed by anaerobic decomposition of organic matter. It produces sulphides and other sludge producing substances. Blue-green algae can grow under such circumstances.
- Stink comes from anaerobic breakdown products of organic matter. The toxins released by blue-green algae further deteriorate the quality of water causing sickness and skin rashes in animals and humans.
- Sheela could explain to the villagers that deterioration of pond has been due to excess fertilizers used by them in their fields. Rain wash brought these fertilizers into the pond. There was initial spurt in the growth of plants due to this. The phenomenon is called eutrophication. Excess plant matter slowly caused organic loading of water that reduced its oxygen content, killing the fish and other aquatic animals. So fertilizers should be used very judiciously in the fields.
- Carbon dioxide concentration in the atmosphere has reached more than 390 ppm
- The antarctic and arctic waters are becoming acidic causing thinning of animal shells.
- Polar ice is melting,
- Some low lying islands have submerged in sea.
(a) What are the reasons behind all these changes occurring on earth ?
(b) Suggest a mechanism to control the same and if possible to reverse the trend.
(a) The reason for these global changes is faulty recycling of carbon dioxide. More of carbon dioxide is being produced than its consumption in photosynthesis due to
- Excess combustion of fossil fuels in industries, power houses, automobiles, homes and other places,
- Reduced intake of CO2 by plants due to deforestation,
- Higher amounts of CO2 entering the atmosphere not only increases its atmospheric concentration but also the concentration of dissolved CO2 in water, especially in colder seas. This is making colder waters acidic. The acidity is thinning the shells of many marine animals.
- CO2 is a green house gas which is causting global warming. Rise in global temperature is melting snow over poles. This is raising the level of sea water slowly. It was already submerged some low lying islands.
(b) Suggestions :
- Large scale tree plantation in all vacant areas,
- Reduced felling of forest trees.
- Reducing consumption of fossil fuel by reducing dependence on thermal power plants, increasing efficiency of automobiles and switching over to alternate technologies that do not consume fossil fuels.
On a school trip to an industrial estate, students found that the marble used in the office buildings of most factories has lost its shine and become pitted.
- What is the reason of marble pitting
- Can this factor cause harm to vegetation as well ?
- Suggest way to prevent this.
- Pitting and discolouring of marble is due to corrosive action of dry or wet acid rain, comprising sulphur dioxide and nitrogen oxides, emitted during combustion of fossil fuels in industries. The acid reacts with insoluble calcium carbonate of marble and converts it into soluble calcium sulphate and calcium nitrate.
- Yes, Acid rain can also cause harm to vegetation by
- Direct action of acid over plants causing death of leaves,
- Solubilisation of essential minerals and their leaching leaving only toxic minerals in the soil.
- Use of wet scrubbers to remove acidic gases from the industrial emissions.
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