Is Matter Around Us Pure - 2 (Class IX)

Some chalk powder settled at the bottom of a beaker filled with water can be separated from water by decantation and filtration. The chalk powder can then be dried out by evaporation. 

Yes, it is the correct answer as carbon is not a sublimable substance. It does not convert into gas without changing into liquid.

Yes, it is correct. Both a and c are the applications in which chromatography is used.

In chemistry, fractional crystallisation is the method of refining substances based on differences in solubility. If a mixture of two or more substances in solution is allowed to crystallise, e.g. by allowing the temperature of the solution to decrease, the precipitate will contain more of the least soluble substance.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below the triple point of a substance in its phase diagram.

Crystallisation is the process in which crystals of a pure substance are obtained by cooling its hot saturated solution. This technique is used for purification of inorganic/organic solids. This is based upon the principle that when a crystal is formed, it tends to exclude the impurities which remain in the solution.
Centrifugation is the process of separating the suspended particles from a liquid mixture by rotating the mixture at high speed. This technique is based on the fact that denser particles are forced to the bottom and lighter particles stay at the top when spun rapidly.
Sublimation is the process of separating a sublimable volatile component (i.e. substance which changes directly from solid to gas, without going through the intervening liquid state, on heating and vice-versa on cooling) from non–sublimable impurities whereas evaporation is the technique used to separate non–volatile components (solutes) dissolved in volatile solvents, i.e. in this technique, an impure solid is obtained from its solution. 

(1) Separation of cream from milk - Centrifugation
(2) Separation of oil from water - Separating funnel
(3) Separation of pigment from natural colours - Chromatography
(4) Separation of components of air - Fractional distillation

Chemical change is any change that results in the formation of a new chemical substance. It involves making and breaking the bonds between atoms. It cannot be reversed.
Physical change is affecting the form of a chemical substance, but not its chemical composition. It can be reversed. 

Fractional distillation is a technique to separate a mixture of liquids on the basis of the difference in their boiling points. During heating, one and more fraction(s) of the mixture will vapourise.

Chromatography is a method in which sample extract being dissolved in a mobile phase. The mobile phase is then forced through an immobile, immiscible stationary phase. The phases are chosen such that components of the sample have differing solubilities in each phase. A component which is quite soluble in the stationary phase will take longer to travel through it than a component which is not very soluble in the stationary phase, but very soluble in the mobile phase. As a result of these differences in mobilities, sample components will become separated from each other as they travel through the stationary phase. 

Bar magnet is used to separate sand from iron filings.

Immiscible liquids are separated by a separating funnel.

Chemical change is any change that results in the formation of a new chemical substance. It involves making and breaking the bonds between atoms. It cannot be reversed.

Physical change is affecting the form of a chemical substance, but not its chemical composition. It can be reversed.

Denser particles are forced to the bottom and lighter particles stay at the top when spun rapidly irrespective of the direction of the rotation.