4 worked answers · short steps first, explanations when you need them
Exercises and activities
Textbook pages 56–57
Question 1
Choose the correct mineral: (i) formed as a residual mass by decomposition of rocks (ii) leading mineral from Koderma, Jharkhand (iii) minerals accumulated in which rock strata (iv) mineral in monazite sand.
Steps only
(i) Bauxite.
Answer
(i) Bauxite.
(ii) Mica.
(iii) Sedimentary rocks.
(iv) Thorium. These answers follow the mineral examples and deposit types described in the chapter.
Question 2
Answer briefly: (i) distinguish ferrous and non-ferrous minerals and conventional and non-conventional energy (ii) what is a mineral? (iii) how do minerals form in igneous and metamorphic rocks? (iv) why conserve minerals?
Steps only
(i) Ferrous minerals contain iron; non-ferrous minerals do not.
Answer
(i) Ferrous minerals contain iron; non-ferrous minerals do not. Conventional energy sources have long been widely used, such as coal and petroleum; non-conventional sources include solar and wind.
(ii) A mineral is a naturally occurring substance with a definite chemical composition and internal structure.
(iii) As magma cools, minerals crystallise; cracks and veins may fill with minerals from molten or gaseous material.
(iv) Minerals are finite and take very long to form, so careful use preserves them for future needs and reduces environmental harm.
Question 3
Answer in about 120 words: (i) Describe the distribution of coal in India. (ii) Why does solar energy have a bright future in India?
Steps only
(i) Most coal deposits occur in the Gondwana coalfields of the Damodar valley, including Jharkhand and West Bengal, and in the Mahanadi, Godavari, Son and Wardha valleys.
Answer
(i) Most coal deposits occur in the Gondwana coalfields of the Damodar valley, including Jharkhand and West Bengal, and in the Mahanadi, Godavari, Son and Wardha valleys. Tertiary coal occurs in parts of the north-eastern states.
(ii) India receives abundant sunshine over much of the year. Solar energy is renewable and can be generated in remote areas as well as large solar parks. It can reduce reliance on coal and imported fuels and help provide electricity to villages. Costs and storage needs remain challenges, so investment in grids, batteries and responsible land use is important.