What are the favourable qualities given to gold when it is alloyed with copper
or silver for the purpose of making ornaments?
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.
Name the process associated with the following
(a) Dry ice is kept at room temperature and at one atmospheric pressure.
(b) A drop of ink placed on the surface of water contained in a glass spreads
throughout the water.
(c) A potassium permanganate crystal is in a beaker and water is poured
into the beaker with stirring.
(d) A acetone bottle is left open and the bottle becomes empty.
(e) Milk is churned to separate cream from it.
(f) Settling of sand when a mixture of sand and water is left undisturbed
for some time.
(g) Fine beam of light entering through a small hole in a dark room,
illuminates the particles in its paths.
The teacher instructed three students ‘A’, ‘B’ and ‘C’ respectively to prepare
a 50% (mass by volume) solution of sodium hydroxide (NaOH). ‘A’ dissolved
50g of NaOH in 100 mL of water, ‘B’ dissolved 50g of NaOH in 100g of
water while ‘C’ dissolved 50g of NaOH in water to make 100 mL of solution.
Which one of them has made the desired solution and why?
Classify the following as physical or chemical properties
(a) The composition of a sample of steel is: 98% iron, 1.5% carbon and
0.5% other elements.
(b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.
(c) Metallic sodium is soft enough to be cut with a knife.
(d) Most metal oxides form alkalis on interacting with water
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.
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