Page 1 :
Basavarajeswari Public School & College, Ballari, KA 161, , Pure and Mixed substances, , Sub: Chemistry, , Lesson no- 4, , Class : VI Std, , I., Answer the following:, 1. Define the following:, a) Pure substances :- The substance which is made up of only one kind, of molecules and it has definite composition and properties., b) Sublimation :- The process in which a solid change directly into, vapour and vapour changes directly into solid., c) Sedimentation :- The process of allowing the heavy solid particles, settle down at the bottom., d) Decantation :- The process of separating the clear liquid after the, process of sedimentation., e) Floatation :- The process by which we can separate insoluble lighter, solids from the liquid- solid mixture., f) Centrifugation :- The method of separating the fine suspended, particles of a substance in a liquid by rotating the liquid in a closed, container., g) Distillation :- The process of obtaining a pure liquid from a solution, when two liquids differ in their boiling points., h) Chromatography :- A technique used to separate the constituents by, of a mixture by using an adsorbing paper., i) Distillate :- The volatile component of a mixture which is collected in, the flask after distillation., j) Residue :- The solid impurities left on the filter paper., k) Filtrate :- The clear liquid obtained after filtration., l) Volatile Substance :- The substance which evaporate easily.

Page 2 :
2.) Write the difference between homogeneous and heterogeneous, mixtures.., Homogeneous mixture, A mixture in which the, Constituents are distributed, Uniformly., , Heterogeneous mixture, A mixture in which the constituents, Are not distributed uniformly, , 3.) Give two differences between a compound and a mixture., Compound, 1)A substances formed, By the chemical, Combination of two or more, Elements in a definite ratio., 2)The constituent elements, Can be separated by, Chemical method., 3) It is always, Homogeneous, Mixture., , Mixture, A substance formed by the, physical combination of, two or more substances, In any ratio., The constituents are separated, by physical method., It can be homogeneous or, heterogeneous., , 4) Ex :- Water, ammonia., , Ex :- air, sand., , 4) What is loading? Explain the process of loading with an example., Ans:- The process in which an external agent is added to bring the, process of sedimentation is called loading., Alum, Muddy water-----------------(impurities + alum) + clear water, External agent, settles down, 5) Why do we use the following?, a) Filter paper :- It is used for filtration., b) alum :- It is used to bring sedimentation., c) Separating funnel :- It is used to separate two immiscible liquids., d) Sieve :- It is used to separate the bigger components of a mixture., e) Sublimating flask :- It is used for sublimation.

Page 3 :
6) How do you separate a mixture of iron and sulphur?, Ans: Bring a magnet near a mixture of iron and sulphur. Iron will be, attracted by the magnet and sulphur will be separated., 7) How will you separate a mixture of iodine, iron fillings and salt from a, mixture?, Ans: Bring a magnet near a mixture, iron is attracted by a magnet and is, separated. Heat the mixture slightly iodine will be sublimated and thus salt, is left in the flask., 8) Give three reasons why constituents of a mixture are to be separated.,  To remove undesirable material from desirable material.,  Removal of impure substances from pure substances.,  To improve the quality of the substance., 9) Air is a mixture of gases. Give reason., Ans: Because,  The components of air can be separated by physical, method.,  The constituents of air can vary from one place to other.,  The components do not react chemically with one another., II., , Give reasons for the following:, 1) During Churning of milk, cream comes on top., Ans. When milk is rotated at high speed, cream collects in the, centre and being lighter than milk, it floats on the top of mixture., 2)Distilled water is the purest form of water., Ans. Because distilled water is free from the salts and impurities., 3) Iodine, Camphor can be separated from their mixtures by, sublimation., Ans. Because Iodine and Camphor are sublimating substances., 4) Homogeneous mixtures have uniform composition., Ans. Because the constituents of a mixture are distributed, uniformly.

Page 4 :
III., , Find the odd one giving reason., 1) Iodine, Camphor, Naphthalene , iron., Ans. Iron, Except iron, all are sublimating substances., 2) Hand picking, Winnowing, Sieving, Sublimation., Ans. Sublimation, Except this, there is no change in physical state., 3) Solutions, Compound, Suspensions, Emulsions., Ans. Compound, Except this , all are mixtures., 4) Sugar solution, Salt solution, milk, mud solution., Ans. Mud solution, Except this all are homogeneous mixtures., , --------------------------------------------------------------------------------------