class 7

 

 science chapter 2 vedio=

  Q 1. Answer the following questions. (i) What are the three layers of the earth? Answer:  the three layers of earth are : Crust Mantle Core (ii)   What is a rock? Answer:  Any natural mass of mineral matter that makes up the earth’s crust is called a rock. The earth’s crust is made up of various types of rocks of different texture, size and colour. (iii)   Name three types of rocks. Answer:  the three types of rocks are: Igneous Rocks Sedimentary Rocks Metamorphic Rocks (iv)   How are extrusive and intrusive rocks formed? Answer:  The molten lava comes out of volcanoes, reaches the earth’s surface and cools down rapidly to become a solid piece of rock. This is how extrusive rocks are formed. For example – basalt. When the molten lava solidifies deep inside the earth’s crust, the rocks so formed are called intrusive rocks. For example – granite. (v)   What do you mean by a rock cycle? Answer:  The process of transformation of rocks from one type to another, due to changes in certain c

 enviornment  Classification of Resources Resources can be classified in the following ways: (a) On the basis of origin – biotic and abiotic (b) On the basis of exhaustibility – renewable and non-renewable (c) On the basis of ownership – individual, community, national and international (d) On the basis of the status of development – potential, developed stock and reserves (a) On the Basis of Origin – Biotic and Abiotic Biotic Resources  are obtained from the biosphere and have life. Eg: Human beings, flora and fauna, fisheries, livestock etc. Abiotic Resources:  All those things which are composed of non-living things are called abiotic resources. Eg: rocks and metals. (b) On the Basis of Exhaustibility – Renewable and Non-Renewable The resources which can be renewed or reproduced by physical, chemical or mechanical processes are known as  Renewable or Replenishable Resources . The renewable resource may further be divided into continuous or flow. Eg: Solar and wind energy, water, for