Explain why particles of a colloidal solution do not settle down when left
undisturbed, while in the case of a suspension they do.
What would you observe when
(a) a saturated solution of potassium chloride prepared at 60°C is allowed
to cool to room temperature.
(b) an aqueous sugar solution is heated to dryness.
(c) a mixture of iron filings and sulphur powder is heated strongly.
While diluting a solution of salt in water, a student by
mistake added acetone (boiling point 56°C). What technique can be
employed to get back the acetone? Justify your choice.
The ‘sea-water’ can be classified as a homogeneous as well as heterogeneous mixture. Comment.
Salt can be recovered from its solution by evaporation.
Suggest some other technique for the same?
Suggest separation technique(s) one would need to employ to
separate the following mixtures.
(a) Mercury and water
(b) Potassium chloride and ammonium chloride
(c) Common salt, water and sand
(d) Kerosene oil, water and salt
Two chemical species X and Y combine together to form a product P which
contains both X and Y
X + Y → P
X and Y cannot be broken down into simpler substances by simple chemical
reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
(a) (i), (ii) and (iii),
(b) (i), (ii) and (iv)
(c) (ii), (iii) and (iv)
(d) (i), (iii) and (iv)
Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
(a) (i), (ii) and (iii)
(b) (i), (ii) and (iv)
(c) (i), (iii) and (iv)
(d) (ii), (iii) and (iv)
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