(a) Is this a physical or a chemical change?
Ans. Chemical change
(b) Can you prepare one acidic and one basic solution by using the products formed in
the above process? If so, write the chemical equation involved. 

Ans. Acidic and basic solutions can be prepared by dissolving the products of the above
process in water
CaO + H2O → Ca(OH)₂ (basic solution)
CO₂ + H2O → H₂CO₃ (acidic solution)

(a) Name a lustrous non-metal.
Ans. Iodine
(b) Name a non-metal which exists as a liquid at room temperature.
Ans. Bromine
(c) The allotropic form of a non-metal is a good conductor of electricity. Name the
allotrope.
Ans. Graphite
(d) Name a non-metal which is known to form the largest number of compounds.
Ans. Carbon
(e) Name a non-metal other than carbon which shows allotropy.
Ans. Sulphur, phosphorus
(f) Name a non-metal which is required for combustion.
Ans. Oxygen

Ans. Elements: Cu, Zn, O2, F2, Hg, Diamond
Compounds: H2O, CaCO3

(a) Chlorine gas
(b) Potassium chloride
(c) Iron
(d) Iron sulphide
(e) Aluminium
(f) Iodine
(g) Carbon
(h) Carbon monoxide
(i) Sulphur powder

Ans. Chlorine gas, Iron, Aluminium, Iodine, Carbon, Sulphur powder. 

The fractionating column packed with glass beads provides a surface for the vapours to collide and lose energy so that they can be quickly condensed and distilled. Also length of the column would increase the efficiency.

(a) Under which category of mixtures will you classify alloys and why?
(b) A solution is always a liquid. Comment.
(c) Can a solution be heterogeneous?

Ans. (a) Homogenous mixture, because they have a uniform composition throughout
(b) No, solid solutions and gaseous solutions are also possible. Examples brass and air
(c) No, solution is a homogenous mixture of two or more substances 
 

Following reaction takes place when part A is heated:
Fe+S →  FeS
When dil. Hydrochloric acid is added to iron sulphide, following reaction takes place and hydrogen sulphide gas is evolved.

FeS + 2HCI →  FeCI₂  + H₂S
Hydrogen sulphide is a foul smelling gas and smells like rotten egg. When dil. Hydrochloric acid is added to the mixture of iron and Sulphur, following reaction takes place and hydrogen gas is evolved.

Fe + S → 2HCI → FeCI + H_{2 +} S

In this case, Sulphur does not participate in the reaction.
When a burning matchstick is brought near the evolved gas the matchstick burns with a pop sound. This confirms the evolution of hydrogen gas.

A child wanted to separate the mixture of dyes constituting a sample of ink. He marked a line by the ink on the filter paper and placed the filter paper in a glass containing water as shown in Fig. 2.3. The filter paper was removed when the
water moved near the top of the filter paper.
(i) What would you expect to see, if the ink contains three different coloured components?
(ii) Name the technique used by the child.
(iii) Suggest one more application of this technique. 

Ans. (i) Three different bands will be observed.
(ii) Chromatography
(iii) To separate the pigments present in Chlorophyll.