Points to Remember: Carbon occurs in the earth’s crust in free as well as in combined state. In free state, it occurs as coal, diamond and graphite. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food nutrients and carbonates. Diamond is the hardest naturally occurring substance known. Fullerenes are discovered only recently. EXERCISE – I Question 1. FILL IN THE BLANKS. (a) Carbon is present in both living and non-living things. (b) The tendency of an element to exist in two or more forms but in the same physical state is called Allotropy . (c) Diamond and Graphite are the two major crystalline allotropes of carbon. (d) Diamond is the hardest substance that occurs naturally. (e) The name ‘carbon’ is derived from the Latin word carbo . Question 2. CHOOSE THE CORRECT ALTERNATIVE. (a) In combined state, carbon occurs as (i) coal (ii) diamond (iii) graphite (iv) petroleum (b) A crystalline form of carbon is (i) lampblac...
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