CBSE Class 10 Answered
(a)Amphoteric oxides are those oxides which show properties of both acids as well as bases to form salts and water.
Ex: Aluminium oxide(Al2O3) and ZnO are examples of amphoteric oxides.
(b) Metals such as Sodium and Potassium are kept immersed is Kerosene because they are very reactive and have high affinity towards oxygen and will violently react with atmospheric oxygen on contact with air.
(c) Aluminium reacts readily with steam to give aluminium oxide and hydrogen gas. The reaction does not always occur. This is due to a thin but strong layer of aluminium oxide being coated onto the metal, thus preventing it from the reaction.
Aluminium + Steam → Aluminium oxide + Hydrogen
2Al(s) + 3H2O(g) → Al2O3(s) + 3H2(g)
(d) (i) Non-metal which is a liquid at room temperature - Bromine
(ii) Non-metal which is lustrous - Iodine
OR
(a)Diamond and graphite are the two allotropes of carbon.
Diamond -
(i) hardest substance
(ii) electrical insulator
Graphite -
(i) comparatively soft, it is slippery over layers
(ii) good electrical conductor
(b)Aluminium articles have a longer life and attractive finish compared to many other metals because of the formation of a thin transparent protective film cover of Aluminium oxide on the surface of Al formed due to its spontaneous reaction with oxygen.
(c)
(i) Ore : An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element(s).
(ii) Gangue: In mining,earthly impurities including silica, mud etc. associated with the ore are called gangue.
(d) Electronic configuration of metal atom tells us about the type of bond the metal will be forming.
For example: In the formation of calcium chloride, chlorine only needs one electron to complete its octet so two atoms of chlorine accept one electron each lost by calcium atom.