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.
Solution
(a)Aluminium is metal that is malleable, soft and doesn't react with food. It also helps to retain the moisture in the food. (b) Metals are good heat and electrical conductors, so they can use electricity to heat up and then transmit the heat to a liquid. (c) Copper is less reactive than zinc. A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal. Thus, copper can't replace zinc from zinc sulphate solution. (d) Sodium and potassium metals are very reactive. They react vigorously with oxygen and water. A lot of heat is generated in the reaction. They are, therefore, stored in kerosene.
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