Give reasons: Platinum, gold and silver are used to make jewellery.

Platinum, gold and silver are used to make jewellery because they are highly malleable and ductile as well as lustrous. They are also less reactive and do not get corroded easily. They are placed towards the bottom in the reactivity series of metals.

Food cans are coated with tin and not with zinc because

zinc has a higher melting point than tin

Explain electrolytic refining used for refining of metals.

The process of purifying impure metal is called refining of metal. Electro-refining is one of the methods of refining of metals. The impure metal is made the anode, while a thin sheet of pure metal is made the cathode. The electrolyte used, is a salt solution of a metal, which is to be refined. Pure metal deposits at the cathode and impurities settle down forming anode mud. Metals like copper, aluminium and zinc are refined by this process.

Define the following term with example. Ore

Minerals that contain a very high percentage of a particular metal (and a low percentage of impurities) and from which the metal can be easily and profitably extracted, are called ores. Example: Ores of iron are Haematite, Magnetite, Siderite, Iron pyrites. The process of obtaining metals from ores is known as the extraction of metals or metallurgy.