Q5.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 solution. (d) Sodium and potassium are stored in kerosene.
(e) Lemon pickle cannot be stored in a metal utensil.
Q5.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 solution. (d) Sodium and potassium are stored in kerosene.
(e) Lemon pickle cannot be stored in a metal utensil.
1.Aluminium is a good conductor of heat and at the same time it is poor radiator of heat. once we wrap hot food in the aluminium foil it keeps the food warm.More over it is malleable and cost-effective so it is widely used in packaging of food.
2.Immersion rod is made up of metal because metals are good conductor of heat so they heat up easily and made surrounding water hot.
3. copper can not displace zinc from its solution as copper is less reactive than zinc.Only more reactive metals can displace less reactive metals from their solutions.
4.It reacts readily with atmospheric oxygen and and turns into Na2O and K2O.The free Na and K catch fire and starts burning if kept open. Even they vigorously reacts with water also so they are kept in kerosine.
5.Metals react with acid to change the composition. Lemon pickles being acidic in nature will react with metal container when kept in it and hence the taste and quality of pickle will change. Therefore lemon pickles are not stored in metal containers.
1.Aluminium is a good conductor of heat and at the same time it is poor radiator of heat. once we wrap hot food in the aluminium foil it keeps the food warm.More over it is malleable and cost-effective so it is widely used in packaging of food.
2.Immersion rod is made up of metal because metals are good conductor of heat so they heat up easily and made surrounding water hot.
3. copper can not displace zinc from its solution as copper is less reactive than zinc.Only more reactive metals can displace less reactive metals from their solutions.
4.It reacts readily with atmospheric oxygen and and turns into Na2O and K2O.The free Na and K catch fire and starts burning if kept open. Even they vigorously reacts with water also so they are kept in kerosine.
5.Metals react with acid to change the composition. Lemon pickles being acidic in nature will react with metal container when kept in it and hence the taste and quality of pickle will change. Therefore lemon pickles are not stored in metal containers.
