CBSE Class 10 Science 2019 · Paper 31/2/1 · Question 4(a)
Give reasons :
- (a)Platinum, gold and silver are used to make jewellery.
- (b)Metals like sodium and potassium are stored under oil.
Answer
Platinum, gold and silver are lustrous, malleable and very unreactive; sodium and potassium are highly reactive, so they are kept under oil.
(a) Platinum, gold and silver are lustrous (shiny) and highly malleable and ductile, so they can be worked into fine ornaments, and they are among the least reactive metals, hardly attacked by air and water (silver only tarnishes slowly), so they stay bright for a long time.
(b) Sodium and potassium are highly reactive: they react vigorously with the oxygen and moisture of the air and catch fire if kept in the open. They are kept immersed in kerosene (oil) so that air and moisture cannot reach them.
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