CONCERNS ABOUT OUR ENVIRONMENT ~ PHYSICAL SCIENCE Chapter 1(class 10 wbbse) ( Important Short questions & Notes )

MADHYAMIK  PHYSICAL SCIENCE 

  SUGGESTION

 CONCERNS ABOUT OUR ENVIRONMENT ~ PHYSICAL SCIENCE 

1) Mention one harmful effect of global warming.

Ans. As a direct consequences,  the polar ice caps will melt. So the water level in the oceans will rise and several coastal cities will submerge.

2) What is the main constitutent of Biogas? 

Ans. Methane

3) Name the fuel which has the highest calorific value.

Ans.Hydrogen gas

4) In which zone of the atmosphere temperature increases with the increasing altitude?

Ans. Stratosphere 

5) What is meant by calorific or heating value  of fuel ?

Ans. The amount of heat generated on complete combustion of 1 kilogram fuel is called the heating value or calorific value of that particular fuel.

It is generally expressed in Units of kilocalorie per kg or kilojoule per kg or kilojoule per gram etc.

6) Which atom , released from a chloroflurocarbon   under the influence of UV rays, decomposes ozone into oxygen? 

Ans. CFCs are broken down by UV radiation to form free Cl atom.

7) Which of the light energy received from the sun has the shortest wavelength?  

Ans. Ultraviolet light 

8) What kind of energy transformation take place at a thermal power station?  

Ans. Chemical energy into electrical energy. 

9) Name one source of energy which is not derived directly or indirectly from solar energy.

Ans. Geothermal energy.

10) What is the full form of CFC ? 

Ans. Chlorofluorocarbons

11) What is stratopause ? 

Ans. The region above stratosphere i.e. above 50 km is called stratopause.

12) Name two gases other than carbon dioxide that are given out during burning of fossil fuel and contribute towards acid rain. 

Ans. NO2 and SO2 

13) Name any two radiation emitted by the sun that are not visible to human eye ? 

Ans. Infrared radiation and Ultraviolet radiation 

14) What is the full form CNG? 

Ans. Compressed Natural Gas.

15) Which of the following produces more heat ( per unit mass ) on burning - Coal or LPG ?

Ans. LPG

16) What is the full form of LPG ? 

Ans. Liquefied petroleum gas

17) Name the original source of wind energy? 

Ans. Sun

18) Name the agent which decomposes animal dung into biogas ? 

Ans. Anaerobic bacteria 

19) What is the full form of OTE ? 

Ans. Ocean Thermal Energy 

20) Name good domestic fuel ? 

Ans. Biogas 

21) What is the value of solar constant? 

Ans. 1.4 kw/m^2

22) What is the minimum wind speed required for running an wind mill ? 

Ans. 10km/hr

23) Name a conventional source of energy. 

Ans. Solar energy 

24) Upto how much height over the earth our atmosphere extends?  

Ans. 500km

25) What is CBM ?

Ans. Coal bed methane (CBM) is an unconventional form of natural gas found in coal deposits or coal seams. It is a primary clean energy source of natural gas.

26) What is Bio - mass ?

Ans. Biomass is the fuel developed from organic matter waste of living organisms like plant waste, animal waste, forest waste, and municipal wastes.

27) Mention some disadvantages of Bio - mass.

Ans. If crops are no longer grown then there wouldn't be any agricultural waste found. If there’s a demand for biomass then harvesting methods need to be developed. Another major disadvantage is that the land used for growing crops for biomass, is occupied for the long term and which may be used for other purposes like housing, conservation, farming,  resort or agricultural use.

28) Compare Biomass and Biogas ? 

Ans.

29) What is Homosphere ?

Ans. ( 'Homo' means same and 'sphere' means region ) - The composition of the atmosphere from the earth's surface to nearly 90 kms above is formed of the same proportion of the various gases found in the atmosphere. This layer of the atmosphere is , therefore,  called the Homosphere.

30) What is Heterosphere ?

Ans. ( 'Hetero' means variable and and 'sphere' means region )- Above the Homosphere till nearly 10000 kms above stretches the Heterosphere. In this layer the proportions of the various gases are not the same and the layers of these various gases do not maintain the same distances (i.e. width).

31) State some anthropogenic sources of methane. 

Ans. Methane  (CH4) : Release from production of cooking / natural gas, oil or coal or their transmission 

Enteric fermentation from ruminants  (e.g. cattle , sheep, goats )

Wetland rice cultivation 

Landfill waste sites 

Burning and decay of biomass

32) What is the importance of water vapour in atmosphere?  

Ans. a. Presence of water vapour in the air causes clouds to form and rain to occur. 

b. Another name of water is life , as it sustains life. 

c. Water vapour in its various forms, like dew, fog , hail , snow etc. has an important role to play in determining the climate of a place.

Heavy rainfall areas have humid climate,  while low rainfall areas or areas of low water vapour form desert climate.

35) What is the impact of global warming on crop yield?  

Ans. Crop yield is expected to increase upto 60-80 percent in some areas because of rise in CO2 level. However, other factors can offset these effects. It is also predicted that regional climate changes in many ecosystems will happen. Therefore,  pattern of agricultural chancges , or eff9on ecosystems in general are fairly unpredictable.

36) How is photovoltaic technology used for harnessing energy?  

Ans. It involves the direct conversion of solar radiation into direct current  (DC) electricity. It was Albert Einstein who discovered that tiny particles of light known as photons (symbolized as hv ) can excite electrons from lower energy band to a higher energy band. In this excited state , electrons can be separated from parent atoms to produce electric current. Semi conducting materials are the most effective in this process of photoconversion.

37) Why are fossil fuels called non renewable resources?  

Ans. An important aspect relating to fossil fuels is that they have required millions of years to accumulate, whereas they are being used up at an alarming rate by human society.The fossil fuels are non - renewable resources.  Once they are gone , there will not be more,  since they are produced in thousands of years by geologic processes.

38) Analyse the relationship between air temperature and air pressure.

Ans. Air pressure is intensely related to air temperature. When air is 

Heated,  it expands and becomes light. Over a warm region of the earth,  heated air expands and rises up and after being overflown aloft,  it moves towards regions of lower temperature. The obvious result is that the weight of air is reduced in the warm region and increased in the adjacent cooler region. 

The general principle is : High temperatures tend to produce low sea level pressure;  low temperatures produce high sea level pressure.

39) What are methane hydrates ? 

Ans. Known as flammable ice, methane hydrates are molecules of gas contained in an ice matrix  found in permafrost regions of the arctic and on the sea floor at continental margins below 500 meters of depth. Methane hydrates are subject to research both around their role in the global carbon cycle as well as potential commercial development as an energy resource. Hydrates form along the continental margins at low temperatures and high pressures and are distributed around the world,  many countries have significant resources of them. 

40) How can Coal Bed Methane  (CBM) be harvested for energy? 

Ans. CBM can be recovered from underground coal before , during,  or after mining operations. It can also be extracted from "unminable" coal seams that are relatively deep, thin or of poor or inconsistent quality. Vertical and horizontal wells are used to develop CBM resources. Extraction requires drilling wells into that coal seams and removing water contained in the seam to reduce hydrostatic pressure and release absorbed  (and free) gas out of the coal.

41) How is Ozone layer formed ? 

Ans. Ozone is an allotrope of oxygen,  its molecule contains three oxygen atoms (O3). In the upper region of stratosphere  (16-40)km ozone is continuously being formed by the absorption of short wavelength ultraviolet  (UV) radiations. Ultraviolet radiations decompose molecular oxygen to atomic oxygen by photolytic decomposition.

42) What do you mean by inversion of temperature ?

Ans. Under normal condition, the temperature decreases with increasing height at the rate of 1°C per 167 metres. This is known as normal lapse rate.

But sometimes,  the conditions are reversed when the temperature increases with height locally and temporarily. This condition in which the colder air is nearer the earth keeping the warmer air above , is called inversion of temperature.

43) What is the influence of dust particles on atmosphere?  

Ans. i) Scientists have concluded after conducting tests that the floating dust particles in the atmosphere form hygroscopic nuclei or nuclei on the particle on which water vapour condenses to water to  form droplets of water, forming clouds,  fogs, etc.

ii) Dust particles get directly heated by the short wave radiation or insolation from the sun and heat the atmosphere affecting the distribution of solar energy on the earth's surface.

iii) The sky looks coloured due to the presence of dust particles. Though blue colour predominantes, the various colours are seen in the sky because the dust particles act as reflectors , refractors or prism causing waves of various colours. Without dust particles in the sky , during day also the sky would have been in darkness. According to many scientists,  disasters can occur from dust particles in the atmosphere.

44) What are the advantages of biogas? 

Ans. i) It is clean , non -polluting and cheap.

 ii)It is used directly from the plant and there is no storage problem. 

 iii) The spent slurry is a good fertiliser.

 iv ) Bio gas contains 75% methane,  calorific value of which is very high, so it is a good fuel. 

Bio gas is used for cooking and lighting.

It is good source of renewable energy. It may be used particularly in rural areas for sustainable economic growth.