90 



(c) Hydrogen. 



(1) 



(2) 



(3) 



Source: water. 



Preparation: sulphuric acid and zinc; hydrochloric acid 



and zinc; decomposition of water by electricity. 

 Properties: colorless, odorless, transparent, lightest of 



all bodies, will burn, does not support combustion. 

 (4) Distribution: water, animals and plants. 

 (d) Carbon. 



(1) Sources : carbon dioxide in atmosphere, plants, animals, 



coal, mineral carbonates. 



(2) Preparation: an element in nature diamond, graphite. 



(3) Properties: diamond colorless to black, transparent, 



hardest substance known, refracts light. 

 Graphite black, soft, crumbly. 



3. Cooling of Nebular Mass. 



(a) Contraction due to radiation of heat. 



(b) Kevolution result of contraction. 



(c) Centrifugal force due to revolution. 



4. Forces Acting in Nebular Mass. 



(a) Cohesive. 



(b) Gravitative. 



(c) Centrifugal. 



Give simple experiments which will illustrate 



(a) Cohesion of gases, liquids and solids. 



(b) Law of gravitation; give illustrations. 



(c) Centrifugal force. 



II. Formation of Planets. * 

 Sub-central mass. 



III. The Earth. 

 1. Cooling. 



(a) States of matter: gaseous, liquid, solid due to temperature. 



(b) Effect of heat upon gases, liquids and solids. 



(c) Effect of cold upon gases, liquids, solids. 



