71) Which one of the following represents a chemical change?
(A) Evaporation of alcohol
(B) Sublimation of Iodine
(C) Heating a platinum wire in a bunsen flame
(D) Heating of mercuric oxide powder
72) Nitrogen is prepared in the laboratory by heating:
(A) Ammonium sulphate
(B) Aluminium nitrate
(C) The mixture of ammonium chloride and sodium nitrite
(D) The mixture of ammonium chloride and calcium oxide
73) The material used for bleaching paper pulp is:
(A) Caustic soda
(B) Sodium
(C) Lime
(D) Alum
74) Which of the following is a gas?
(A) Thorium
(B) Plutonium
(C) Mercury
(D) Chlorine
75) The instrument used for recording tremors of earth is known as:
(A) Crescograph
(B) Lactometer
(C) Seismograph
(D) Hydrometer
76) John Walker invented:
(A) Safety match
(B) Safety razor
(C) Safety pin
(D) Safety valve
77) A solid ball of metal has a spherical cavity inside it. If the ball is heated, the volume of the cavity will:
(A) Increase
(B) Decrease
(C) Remain unaffected
(D) Have its shape changed
78) Fat is digested in the:
(A) Mouth
(B) Large intestine
(C) Spleen
(D) Small intestine
79) The phenomenon of mirage is due to:
(A) Change in refractive index of air with change in temperature
(B) Total internal reflection
(C) Polarization of light on reflection
(D) Absorption of light by air at higher temperature
80) A cyclist negotiating a bend, tilts from the vertical direction because of:
(A) Gravitation and friction
(B) Friction and centrifugal force
(C) Gravitation and centrifugal force
(D) Gravitation and centripetal force