6. Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made
up of metallic substances.
(c) Copper cannot displace zinc from its salt so-
lution.
(d) Sodium and potassium are stored in kerosene.
Answers
Answer:
(a) The material used in wrapping food items should be flexible, foldable and non-reactive with the food.
•Aluminum is a soft and malleable metal.
•It can be easily beaten into thin sheets to form wrapping foils.
•Also, aluminum does not react with food items.
Hence, aluminum foils are used to wrap food items.
Hence, aluminum foils are used to wrap food items.
(b) Immersion rods are used for heating liquids.
•The conductivity of heat and electricity of these rods should be good.
•Metallic substances are
•Good conductors of heat and electricity
•Available easily at affordable prices.
Hence, immersion rods for heating liquids are made up of metallic substances.
Hence, immersion rods for heating liquids are made up of metallic substances.
(c)
•Copper is less reactive than zinc.
•In a salt solution,a less reactive metal cannot displace a more reactive metal.
Hence, copper cannot displace zinc from its salt solution.
Hence, copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are very reactive with water, including moisture in the atmosphere.
•They can catch fire even when they come in contact with air.
•Kerosene contains no water and protects these metals from being exposed to any moisture in the air that would cause these metals to react.
Hence, sodium and potassium are stored in kerosene.