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Science scientific reasons[2 marks ]

Materials : Metals and Non-Metals · Bihar Board (BSEB) STD 8 (BSEB - English Medium). 3 questions.

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scientific reasons[2 marks ]

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3 questions · timed · auto-graded

Question 12 Marks
Phosphorus is kept in water.
Answer
$-$Phosphorus is an active non$-$ metal
$-$Phosphorus reacts with oxygen and produces phosphorus pentoxide.
$-$Phosphorus is heavier than water and do not react with water,
$-$So, it cannot react with air if it is kept in water.
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Question 22 Marks
Copper vessel in due course acquires a dull green coating.
Answer
$-$When copper vessels is exposed to moist air for a long time, it reacts with oxygen and carbon dioxide.
$-$During this reaction a layer of mixture of copper hydroxide $[\ce{Ca(OH)_2}]$ and copper carbonate $(\ce{CuCO_3})$ is formed.
$-$The colour of this mixture is green, So, copper vessel in due course acquires a dull green coating.
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Question 32 Marks
The use of aluminium has increased over copper for the manufacture of electrical cables.
Answer
$-$Copper and aluminium both metals are good conductors of electricity.
$-$Aluminium is cheaper than copper.
$-$Aluminium is lighter than copper.
$-$So, aluminimum is preferable to copper for manufacturing long distance wires.
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scientific reasons[2 marks ] - Science STD 8 Questions - Vidyadip