Chemistry: Is matter around us Pure?

Identify solute and solvent in 'tincture of iodine'.
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Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do. [NCERT Exemplar]Particle size in a suspension is larger than those in a colloidal solution. Also molecular interaction in a suspension is not strong enough to keep the particles suspended and hence they settle down.Give two examples each for Aerosol, Emulsion.Aerosol: Clouds, smoke Emulsion: Milk, face cream.Smoke and fog both are aerosols. In what way are they different? [NCERT Exemplar]In smoke, the dispersing medium is air and the dispersing phase is solids while in fog, dispersing medium is air and the dispersing phase is liquid.What do you understand by the term distillation? Give its one application.Distillation is the process of separating different miscible liquids from one another by the process of evaporation. It is a process of boiling a liquid and then condensing the vapour obtained into a liquid. The two liquids must have different boiling points. This process is used to obtain wines from the sugarcane juice.Define chromatography and give its one application.Chromatography is the technique used for separation of those solutes that dissolve in the same solvent. It can be used for separation of colors or pigment from natural colour or to separate drugs from blood.Give two points of differences between an element and a compound.Element 1. An element is made up of same kind of atoms. 2. An element cannot be split by physical or chemical methods Compound 1. A compound is obtained from different kinds of atoms 2. A compound can be split into new substances by chemical methods.Identify the dispersed phase and dispersing medium of cheeseCheese— phase: liquid, medium: solidDescribe any three properties of colloid.It is a heterogenous mixture. Size of particles is too small to be seen by naked eye. They scatter light passing through them making its path visible. They do not settle down when left undisturbed. They cannot be separated by the process of filtration, (any three points)What is centrifugation?The principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. It is used for seperating whipped cream from milk.Name a lustrous non-metal.IodineThe allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.GraphiteName a non-metal other than carbon which shows allotropySulphurA solution is always a liquid. Comment.No, solid solutions and gaseous solutions are also possible.Examples are brass, air.Explain why filter paper cannot be used to separate colloids.The size of colloidal particles is less than lnm, while the size of pores present in an ordinary filter paper is larger than lnm. Hence, a colloidal solution cannot be separated by filtration.Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain. [NCERT Exemplar]We cannot separate alcohol dissolved in water by using separating funnel because both the components are highly soluble in each other. They can be separated by fractional distillation.What is the reason for running cold water through condenser from lower side to upper side in distillation process?In distillation process condensation of vapours take place. To absorb more heat, cold water is passed from lower side so that it will stay for longer time and absorb more heat from the vapours to form liquid state of the substance.You are given two samples of water labelled as 'A' and 'B'. Sample 'A' boils at 100°C and sample 'B' boils at 102°C. Which sample of water will not freeze at 0°C? Comment. [ NCERT Exemplar]Sample 'B' will not freeze at 0°C because it is not pure water. At 1 atm, the boiling point of pure water is 100°C and the freezing point of pure water is 0°C.