(i)A colourless gas is evolved.
(ii) Test-tube becomes hot.

Evolution shows that body design changed from simple to complex. Hence, bacteria has the simplest body design and chimpanzee has the most complex and better body design.

When the colony of yeast is in water, it does not get nutrition, because water does not have nutrients. Sugar, on the other hand, provides nutrition. Once the yeast gets nutrition, it grows and begins producing buds. That is why, colonies of yeast fail to multiply in water, but multiply in sugar solution.

Bromine solution in CCl₄ has an orange colour. When it is added dropwise to ethene, the orange colour disappears due to the formation of the colourless ethylene dibromide. This reaction is not shown by ethane as it is addition reaction.
\(\mathrm{CH}_2=\mathrm{CH}_2+\mathrm{Br}_2 \longrightarrow \mathrm{CH}_2-\mathrm{CH}_2\)
Ethene          Bromine               |             |
                     (orange               Br           Br
                      colour)            Ethylene dibromide
                                                  (colourless)
The two can be distinguished also by subjecting them to the flame. Saturated hydrocarbon (ethane) generally gives a clear flame while unsaturated hydrocarbon (ethene) gives a yellow flame with lots of black smoke.

Detergents lower the surface tension of water to a greater extent than soaps and hence detergents are better cleansing agents than soaps.

Since compound B has molecular mass 40, it must be sodium hydroxide. When sodium hydroxide is treated with aluminium oxide, it gives sodium aluminate. Then the compound A must be sodium.
A - Sodium Na; B - Sodium hydroxide NaOH; C - Sodium aluminate NaAIO₂.
\(2Na+{ 2H }_{ 2 }O\rightarrow 2NaOH+{ H }_{ 2 }\\ { AI }_{ 2 }{ O }_{ 3 }+2NaOH\rightarrow { 2NaAIO }_{ 2 }+{ H }_{ 2 }O\)

Aquatic organisms like fishes obtain oxygen from water present in dissolved state through their gills. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

When two circular coils A and B placed close to each other and the current in coil A is changed, it leads to induction of current in coil B. This happens because of change in magnetic field of coil A, because of change in current in this coil.

Solder is an alloy of lead and tin. Low melting point of solder makes it suitable for welding electrical wires.

(a) Anode       : Impure silver;
     Cathode     : Pure silver
(b) Electrolyte : Silver salt, such as AgNO₃
(c) We get pure silver at cathode.

(a) Pineal Gland
(b) Pancreas
(c) Adrenal gland
(d) Testis

Synapse is the small gap between two neurons. At the end of axon, the electrical impulse sets the release of some chemicals, which cross the gap (synapse) and start a similar electrical impulse in the dendrite of the next neuron. Synapse actually acts like a one way valve because the chemical substance is present only at one side of the gap.

Egg shells contain calcium carbonate When nitric acid is added to it, carbon dioxide gas is evolved. The reaction can be given as
\(CaCO_3+2HNO_3\rightarrow Ca(NO_3)_2+H_2O+CO_2\)

lons are produced only in aqueous medium and presence of H⁺ ions are responsible for the existence of acidic properties. Hence, acids show acidic behaviour only in the presence of water and not in its absence.