State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s).
Salt can be separated from salt solution by keeping it under the Sun. [ ]
True. When a salt solution is kept under the Sun, the water evaporates due to heat from sunlight, leaving behind the salt. This is the evaporation process used to obtain salt from seawater in shallow pits.
Handpicking should be used only when the quantity of one component is less. [ ]
True. Handpicking is a convenient method when the particles to be removed are present in small quantities and can easily be picked by hand. If the quantity is large, handpicking becomes time-consuming and impractical.
A mixture of puffed rice and rice grains can be separated by threshing. [ ]
False. A mixture of puffed rice and rice grains should be separated by winnowing, not threshing. Threshing is used to separate grains from stalks by beating, while winnowing separates lighter and heavier components by wind or blowing air.
A mixture of mustard oil and lemon water can be separated by decantation. [ ]
True. Oil does not mix with water and forms a separate layer when left undisturbed for some time. The oil layer can be removed by tilting the vessel, which is the process of decantation.
Sieving is used to separate a mixture of rice flour and water. [ ]
False. Sieving is used to separate solid-solid mixtures based on differences in particle size, not solid-liquid mixtures. A mixture of rice flour and water should be separated by filtration or evaporation.
Explanation
(i) The chapter describes how seawater is kept in shallow pits and exposed to sunlight and air. In a few days, the water evaporates completely, leaving behind the solid mixture from which common salt is obtained. (ii) The chapter states that handpicking proves to be a convenient method if the particles to be removed are present in small quantities and can easily be picked by hand. (iii) The chapter explains that threshing is the process of separating grains from the stalks by beating them on a wooden log. Winnowing is the method of separating lighter and heavier components of a mixture by wind or blowing air. Puffed rice is lighter than rice grains, making winnowing the appropriate method. (iv) The chapter mentions that oil does not mix with water and forms a separate layer when left undisturbed. Decantation is the process of removing the liquid by tilting the vessel after the heavier insoluble component has settled down. (v) The chapter clearly states that sieving is used when components of a solid-solid mixture have different sizes. Rice flour and water form a solid-liquid mixture, which requires filtration or evaporation for separation.