Give reasons for the following. Aluminium foils are used to wrap food items. Immersion rods for heating liquids are made up of metallic substances. Copper cannot displace zinc from its salt solution. Sodium and potassium are stored in kerosene

cbse
cbse-class-8-science
materials-metals
and-nonmetals

#1

Give reasons for the following.

  1. Aluminium foils are used to wrap food items.
  2. Immersion rods for heating liquids are made up of metallic substances.
  3. Copper cannot displace zinc from its salt solution.
  4. Sodium and potassium are stored in kerosene.

Answer:

  1. Aluminium foils are used to wrap food items because aluminium metal is malleable. Therefore, it can be beaten into thin foils.
  2. Metals are good conductors of heat and electricity. Therefore, immersion rods for heating liquids are made of metallic substances.
  3. A metal can displace a less reactive metal from its salt in an aqueous solution.
    But zinc is more reactive than copper. Therefore, copper cannot displace zinc from its salt solution.
    Cu(s) + ZnSO 4(aq)---------► No reaction
  4. Sodium and potassium are stored in kerosene because they are highly reactive elements. They can easily catch fire even when in contact with air.