Thursday, February 7, 2013

CBSE Class 9 - Science - CH 14 Natural Resources (NCERT Q and A)

Natural Resources
(Q & A, NCERT Chapter Solution)
CBSE Class 9 - Science - CH14 - Natural Resources (Worksheet)
Ozone Layer
credits:classroomclipart


Q1: What is lithosphere?

Answer:  The outer crust of the Earth is called the lithosphere.


Q2: What is hydrosphere?

Answer: The water available on the earth's surface as well as underground water comprise together as hydrosphere. Water covers 75% of the Earth's surface.


Q3: What is atmosphere?

Answer: The envelope of air that surrounds the earth is called atmosphere.


Q4: List the four zones of the atmosphere.

Answer: Four zones of atmosphere are:
  1. Tropospshere
  2. Stratosphere
  3. Mesospshere
  4. Thermospshere

Q5:  What is biosphere?

Answer: This life-supporting zone of the Earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible, is known as the biosphere. It accommodates several types of living organisms which remain dependent on natural resources. The biosphere ranges between 6km, above sea level and 10kms below sea.




Q6(NCERT): How is our atmosphere different from the atmosphere on Venus and Mars?

Answer: Earth's atmosphere is quite different from the atmosphere present on Venus and Mars. The atmosphere of the earth consists of Nitrogen(79%), Oxygen(20%), small fraction of carbon dioxide and other gases which make it suitable for living. The atmosphere of Venus or Mars has carbon dioxide as the major component  (95-97%)


Q7(NCERT): How does the atmosphere act as a blanket?

Answer: The atmosphere acts as a blank due to its following functions:
  1. It plays an important role in temperature control. It maintains the average temperature of the earth fairly constant during the course of whole year.
  2. It prevents the sudden increase in temperature during the daylight hours.
  3. During the night, it slows down the escape of heat into outer space.

Q8(NCERT): What causes winds?

Answer: Uneven heating of the earth's surface and water surface causes winds. On heating up the air rises up creating a low pressure region. Air travels from high pressure region to low pressure region forming winds. In addition the rotation of the Earth and the presence of mountain ranges in the paths of the wind also influence to winds.


Q9(NCERT): How are clouds formed?

Answer: Due to various weather phenomena (e.g. uneven heating of land and water bodies on the earth surface), warm and cold convection of air currents generate. Water vapours which are also present in air due to evaporation also rise up. Since air cools down on rising, it leads to condensation of water vapours present in it. Thus vapours condense onto a tiny salt particles called condensation nuclei which form clouds.
Nimbostratus (image credits:wikipedia)

Broadly clouds formed are of four types:
  1. Nimbostratus: (Nimbus means rain). These clouds carry thick precipitation or rains.
  2. Altostratus: These clouds form a foggy, gray and dull weather look.
  3. Cirrostratus: these clouds form fluffy cotton like pattern. 
  4. Cirrus: These are high-level clouds seen during fair weather.

Q10: Which gets heated faster land or water?

Answer: Land


Q11: Define air-pollution?  (Short Answer Q)

Answer: An increase in the content of these harmful substances in air is called air pollution.


Q12(NCERT): List any three human activities that you think would lead to air pollution.

Answer: Three human activities leading to air pollution are:
  1. Rapid urbanization and industrialization.
  2. Deforestation
  3. Burning of fuels like coal and petroleum.
  4. Burning of coal in thermal power plants.

Q13(CBSE 2011): Name two diseases caused due to an increased content of pollutants in the air produced due to the burning of fossil fuels. 

Answer: Bronchitis, asthma, lung cancer.


Q14(CBSE 2011): What is smog?

Answer: Smoke + Fog = Smog. The presence of unburnt hydrocarbons in air when mixed with condensed water vapours forms a thick layer called smog. It lowers the visibility during winter season and is an indication of air pollution.


Q15: How do fossil fuel cause air pollution?

Answer: The fossil fuels like coal and petroleum contain traces of nitrogen and sulphur. When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur. These oxides of nitrogen and sulphur are poisonous and can cause respiratory problems. These oxides when mix with rain water give rise to acid water due to formation of nitric and sulphuric acids.


Q16(Value Based): Meenakshi saw reduction in greenish layer of lichens at the bark of trees at the biology garden of the school. The garden was few metres away from diesel generator placed for electricity backup. She immediately informed the school authorities to check the pollution level of diesel and kerosene used in the generator. 

(a) How reduction in Lichens layer is related to pollution?
(b) What measures should be taken by school authorities to check the reduction?
(c) What qualities are shown by Meenakshi by informing school about the Lichens?

Answer:
(a) Lichens are found to be very sensitive to the levels of contaminants like sulphur dioxide in
the air. Diesel and Kerosene contain traces of nitrogen and sulphur which for deadly oxides when mised in air.

(b)  School authorities should check the pollution level and quality of fuel used in diesel generator. They should also replace the generator with a better which does not pollute the environment. The generator should be place away from the school premises to avoid inhalation of smoke from it.

(c) She is concerned about air pollution and showed her social responsibility to keep the environment clean and pollution free.


Q17: Give an example of fungi which are known as 'indicator of air pollution'.

Answer: Lichens.


Q18(NCERT): Why do organisms need water?
OR
Q(NCERT): Why is water essential for life?
OR
Q(CBSE 2011): Water is known as ‘A Wonder Liquid’. Justify this statement by giving any two reasons.

Answer:  Water is an essential part for living organisms:
  • Most of the biochemical processes involve water e.g. photosynthesis takes water as one of the raw material to prepare food.
  • The major component of blood is water (plasma) which helps in transportation of food and excretory substances.
  • Water is used as part of food as a source of energy.
  • Water in sweat cools down the body temperature. Similarly water as transpiration loss in plants controls temperature of the plant as well as it helps in ascent of sap.
  • Water is used in many activities like drinking, food preparation, irrigation, power generation and industries.
  • Water is an essential medium for aquatic life. Amphibians also need water to carry out reproduction.
  • Water is a universal solvent hence it is used in medicines and a many chemical reactions takes place when dissolved in water.
  • Water makes up 70% of body weight of human beings and it carries out various metabolic activities in all animals. 

Q19: What are the effects of acid rain?

Answer:  Effects of acid rain are:
  • Acidification of soil reduces fertility of soil.
  • Destroys aquatic life and pollutes water resources. 
  • Causes irritation to eyes and skins of human beings and cattle.
  • Causes corrosion to buildings, bridges, statues etc.

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