Q15 of 27 Page 1

What is a dam? Why do we seek to build large dams? While building large dams, which three main problems should particularly be addressed to maintain peace among local people? Mention them.

•A dam is a barrier constructed to hold back water and raise its level to form a reservoir.


•We seek to build large dams so that they can be used to generator electricity and be as a water supply for irrigation purposes.


•When building dams some things need to be kept in mind.


•Dams cannot be constructed everywhere. They’re often constructed in hilly terrains.


•Dam construction leads to a loss of a large amount of agricultural land, so when constructing dams, this should be kept in mind.


•Construction of dams also leads to destruction of habitats as lands get submerged in water. So some kind of rehabilitation process needs to be in effect.


•Also, there needs to be some form of compensation and rehabilitation facility in place for local people because construction of dams leads to displacement of the local population.


More from this chapter

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13

A. List the factors on which the resistance of a conductor in the shape of a wire depends.

B. Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason.


 14

Students in a school listened to the news read in the morning assembly that the mountain of garbage in Delhi, suddenly exploded and various vehicles got buried under it. Several people were also injured and there was traffic jam all around. In the brain storming session the teacher also discussed this issue and asked the students to find out a solution to the problem of garbage. Finally they arrived at two main points– one is self management of the garbage we produce and the second is to generate less garbage at individual level.

(a) Suggest two measures to manage the garbage we produce.


(b) As an individual, what can we do to generate the least garbage? Give two points.


(c) List two values the teacher instilled in his students in this episode.


 16

(a) Write the steps involved in the extraction of pure metals in the middle of the activity series from their carbonate ores.

(b) How is copper extracted from its sulphide ore? Explain the various steps supported by chemical equations. Draw labelled diagram for the electrolytic refining of copper.


 17

(a) The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.

(b) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.


(c) State Modern periodic law.