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No. General Knowledge Question Answer

1 The first Prime minister of India was Pt. Jawahar Lal Nehru

2 The longest river in the world is the Nile

3 The longest highway in the world is the Trans-Canada

4 The longest highway in the world has a length of About 8000 km

5 The highest mountain in the world is the Mount Everest

6 The country that accounts for nearly one third of the total teak production of the world is Myanmar

7 The biggest desert in the world is the Sahara desert

8 The largest coffee growing country in the world is Brazil

9 The country also known as "country of copper" is Zambia

10 The name given to the border which separates Pakistan and Afghanistan is Durand line

11 The river Volga flows out into the Caspian sea

12 The coldest place on the earth is Verkoyansk in Siberia

13 The country which ranks second in terms of land area is Canada

14 The largest Island in the Mediterranean sea is Sicily

15 The river Jordan flows out into the Dead sea

16 The biggest delta in the world is the Ganges Delta

17 The capital city that stands on the river Danube is Belgrade

18 The Japanese call their country as Nippon

19 The length of the English channel is 564 kilometres

20 The world's oldest known city is Damascus

21 The city which is also known as the City of Canals is Venice

22 The country in which river Wangchu flows is Myanmar

23 The biggest island of the world is Greenland

24 The city which is the biggest centre for manufacture of automobiles in the world is Detroit, USA

25 The country which is the largest producer of manganese in the world is China & South Africa

26 The country which is the largest producer of rubber in the world is Malaysia

27 The country which is the largest producer of tin in the world is China

28 The river which carries maximum quantity of water into the sea is the Amazon River

29 The city which was once called the `Forbidden City' was Peking

30 The country called the Land of Rising Sun is Japan

31 Mount Everest was named after Sir George Everest

32 The volcano Vesuvius is located in Italy

33 The country known as the Sugar Bowl of the world is Cuba

34 The length of the Suez Canal is 162.5 kilometers

35 The lowest point on earth is The coastal area of Dead sea

36 The Gurkhas are the original inhabitants of Nepal

37 The largest ocean of the world is the Pacific ocean

38 The largest bell in the world is the Tsar Kolkol at Kremlin, Moscow

39 The biggest stadium in the world is the Strahov Stadium, Prague

40 The world's largest diamond producing country is South Africa

41 Australia was discovered by James Cook

42 The first Governor General of Pakistan is Mohammed Ali Jinnah

43 Dublin is situated at the mouth of river Liffey

44 The earlier name of New York city was New Amsterdam

45 The Eiffel tower was built by Alexander Eiffel

46 The Red Cross was founded by Jean Henri Durant

47 The country which has the greatest population density is Monaco

48 The national flower of Britain is Rose

49 Niagara Falls was discovered by Louis Hennepin

50 The national flower of Italy is Lily

51 The national flower of China is Narcissus

52 The permanent secretariat of the SAARC is located at Kathmandu

53 The gateway to the Gulf of Iran is Strait of Hormuz

54 The first Industrial Revolution took place in England

55 World Environment Day is observed on 5th June

56 The first Republican President of America was Abraham Lincoln

57 The country famous for Samba dance is Brazil

58 The name of Alexander's horse was Beucephalus

59 Singapore was founded by Sir Thomas Stamford Raffles

60 The famous British one-eyed Admiral was Nelson

61 The earlier name of Sri Lanka was Ceylon

62 The UNO was formed in the year 1945

63 UNO stands for United Nations Organization

64 The independence day of South Korea is celebrated on 15th August

65 'Last Judgement' was the first painting of an Italian painter named Michelangelo

66 Paradise Regained was written by John Milton

67 The first President of Egypt was Mohammed Nequib

68 The first man to reach North Pole was Rear Admiral Robert E. Peary

69 The most famous painting of Pablo Picasso was Guermica

70 The primary producer of newsprint in the world is Canada

71 The first explorer to reach the South Pole was Cap. Ronald Amundson

72 The person who is called the father of modern Italy is G.Garibaldi

73 World literacy day is celebrated on 8th September

74 The founder of modern Germany is Bismarck

75 The country known as the land of the midnight sun is Norway

76 The place known as the Roof of the world is Tibet

77 The founder of the Chinese Republic was San Yat Sen

78 The first Pakistani to receive the Nobel Prize was Abdul Salam

79 The first woman Prime Minister of Britain was Margaret Thatcher

80 The first Secretary General of the UNO was Trygve Lie

81 The sculptor of the statue of Liberty was Frederick Auguste Bartholdi

82 The port of Baku is situated in Azerbaijan

83 John F Kennedy was assassinated by Lee Harvey Oswald

84 The largest river in France is Loire

85 The Queen of England who married her brother-in-law was Catherine of Aragon

86 The first black person to be awarded the Nobel Peace Prize was Ralph Johnson Bunche

87 The first British University to admit women for degree courses was London University

88 The principal export of Jamaica is Sugar

89 New York is popularly known as the city of Skyscrapers

90 Madagascar is popularly known as the Island of Cloves

91 The country known as the Land of White Elephant is Thailand

92 The country known as the Land of Morning Calm is Korea

93 The country known as the Land of Thunderbolts is Bhutan

94 The highest waterfalls in the world is the Salto Angel Falls, Venezuela

95 The largest library in the world is the United States Library of Congress, Washington DC

96 The author of Harry Potter Books is JK Rowling

97 Nickname of New York city is Big Apple

98 What do you call a group of sheep? A Flock of Sheep

99 In which sport do players take long and short corners? Hockey

100 Who was the youngest President of the USA? Theodore Roosevelt

101 How many legs do butterflies have? 6 Legs & 2 Pair of Wings

102 Who invented the Nintendo Wii? Kashi Kabushiki

103 What year does the Nintendo Wii come out? Late 2006

104 Who invented the Light Bulb? Humphry Davy

105 Who invented the washing machine? James King

106 Who invented the first electric washing machine? Alva Fisher

107 Who invented the safety pin? Walter Hunt

108 Who invented the Vacuum Cleaner? Hubert Booth

109 Who won the Football World Cup in 2006? Italy

110 Which country hosted the Football World Cup in 2006? Germany

No.	General Knowledge Question	Answer
1	The first Prime minister of India was	Pt. Jawahar Lal Nehru
2	The longest river in the world is the	Nile
3	The longest highway in the world is the	Trans-Canada
4	The longest highway in the world has a length of	About 8000 km
5	The highest mountain in the world is the	Mount Everest
6	The country that accounts for nearly one third of the total teak production of the world is	Myanmar
7	The biggest desert in the world is the	Sahara desert
8	The largest coffee growing country in the world is	Brazil
9	The country also known as "country of copper" is	Zambia
10	The name given to the border which separates Pakistan and Afghanistan is	Durand line
11	The river Volga flows out into the	Caspian sea
12	The coldest place on the earth is	Verkoyansk in Siberia
13	The country which ranks second in terms of land area is	Canada
14	The largest Island in the Mediterranean sea is	Sicily
15	The river Jordan flows out into the	Dead sea

16	The biggest delta in the world is the	Ganges Delta
17	The capital city that stands on the river Danube is	Belgrade
18	The Japanese call their country as	Nippon
19	The length of the English channel is	564 kilometres
20	The world's oldest known city is	Damascus
21	The city which is also known as the City of Canals is	Venice
22	The country in which river Wangchu flows is	Myanmar
23	The biggest island of the world is	Greenland
24	The city which is the biggest centre for manufacture of automobiles in the world is	Detroit, USA
25	The country which is the largest producer of manganese in the world is	China & South Africa
26	The country which is the largest producer of rubber in the world is	Malaysia
27	The country which is the largest producer of tin in the world is	China
28	The river which carries maximum quantity of water into the sea is the	Amazon River
29	The city which was once called the `Forbidden City' was	Peking
30	The country called the Land of Rising Sun is	Japan
31	Mount Everest was named after	Sir George Everest
32	The volcano Vesuvius is located in	Italy
33	The country known as the Sugar Bowl of the world is	Cuba
34	The length of the Suez Canal is	162.5 kilometers
35	The lowest point on earth is	The coastal area of Dead sea
36	The Gurkhas are the original inhabitants of	Nepal
37	The largest ocean of the world is the	Pacific ocean
38	The largest bell in the world is the	Tsar Kolkol at Kremlin, Moscow
39	The biggest stadium in the world is the	Strahov Stadium, Prague
40	The world's largest diamond producing country is	South Africa
41	Australia was discovered by	James Cook
42	The first Governor General of Pakistan is	Mohammed Ali Jinnah
43	Dublin is situated at the mouth of river	Liffey
44	The earlier name of New York city was	New Amsterdam
45	The Eiffel tower was built by	Alexander Eiffel
46	The Red Cross was founded by	Jean Henri Durant
47	The country which has the greatest population density is	Monaco
48	The national flower of Britain is	Rose
49	Niagara Falls was discovered by	Louis Hennepin
50	The national flower of Italy is	Lily
51	The national flower of China is	Narcissus
52	The permanent secretariat of the SAARC is located at	Kathmandu
53	The gateway to the Gulf of Iran is	Strait of Hormuz
54	The first Industrial Revolution took place in	England
55	World Environment Day is observed on	5th June
56	The first Republican President of America was	Abraham Lincoln
57	The country famous for Samba dance is	Brazil
58	The name of Alexander's horse was	Beucephalus
59	Singapore was founded by	Sir Thomas Stamford Raffles
60	The famous British one-eyed Admiral was	Nelson
61	The earlier name of Sri Lanka was	Ceylon
62	The UNO was formed in the year	1945
63	UNO stands for	United Nations Organization
64	The independence day of South Korea is celebrated on	15th August
65	'Last Judgement' was the first painting of an Italian painter named	Michelangelo
66	Paradise Regained was written by	John Milton
67	The first President of Egypt was	Mohammed Nequib
68	The first man to reach North Pole was	Rear Admiral Robert E. Peary
69	The most famous painting of Pablo Picasso was	Guermica
70	The primary producer of newsprint in the world is	Canada
71	The first explorer to reach the South Pole was	Cap. Ronald Amundson
72	The person who is called the father of modern Italy is	G.Garibaldi
73	World literacy day is celebrated on	8th September
74	The founder of modern Germany is	Bismarck
75	The country known as the land of the midnight sun is	Norway
76	The place known as the Roof of the world is	Tibet
77	The founder of the Chinese Republic was	San Yat Sen
78	The first Pakistani to receive the Nobel Prize was	Abdul Salam
79	The first woman Prime Minister of Britain was	Margaret Thatcher
80	The first Secretary General of the UNO was	Trygve Lie
81	The sculptor of the statue of Liberty was	Frederick Auguste Bartholdi
82	The port of Baku is situated in	Azerbaijan
83	John F Kennedy was assassinated by	Lee Harvey Oswald
84	The largest river in France is	Loire
85	The Queen of England who married her brother-in-law was	Catherine of Aragon
86	The first black person to be awarded the Nobel Peace Prize was	Ralph Johnson Bunche
87	The first British University to admit women for degree courses was	London University
88	The principal export of Jamaica is	Sugar
89	New York is popularly known as the city of	Skyscrapers
90	Madagascar is popularly known as the Island of	Cloves
91	The country known as the Land of White Elephant is	Thailand
92	The country known as the Land of Morning Calm is	Korea
93	The country known as the Land of Thunderbolts is	Bhutan
94	The highest waterfalls in the world is the	Salto Angel Falls, Venezuela
95	The largest library in the world is the	United States Library of Congress, Washington DC
96	The author of Harry Potter Books is	JK Rowling
97	Nickname of New York city is	Big Apple
98	What do you call a group of sheep?	A Flock of Sheep
99	In which sport do players take long and short corners?	Hockey
100	Who was the youngest President of the USA?	Theodore Roosevelt
101	How many legs do butterflies have?	6 Legs & 2 Pair of Wings
102	Who invented the Nintendo Wii?	Kashi Kabushiki
103	What year does the Nintendo Wii come out?	Late 2006
104	Who invented the Light Bulb?	Humphry Davy
105	Who invented the washing machine?	James King
106	Who invented the first electric washing machine?	Alva Fisher
107	Who invented the safety pin?	Walter Hunt
108	Who invented the Vacuum Cleaner?	Hubert Booth
109	Who won the Football World Cup in 2006?	Italy
110	Which country hosted the Football World Cup in 2006?	Germany

1. Question: A man with a load jumps from a high building. What will be the load experienced by him?

Answer: Zero, because while falling, both the man and the load are falling at the same acceleration i.e. acceleration due to gravity.
Question:2. Question: A piece of chalk when immersed in water emits bubbles. Why?
Answer: Chalk consists of pores forming capillaries. When it is immersed in water, the water begins to rise in the capillaries and air present there is expelled in the form of bubbles. Question:3. Question: Why does a liquid remain hot or cold for a long time inside a thermos flask?
Answer: The presence of air, a poor conductor of heat, between the double glass wall of a thermos flask, keeps the liquid hot or cold inside a flask for a long time.
Question:4. Question: Why does a ball bounce upon falling?
Answer:When a ball falls, it is temporarily deformed. Because of elasticity, the ball tends to regain its original shape for which it presses the ground and bounces up (Newton's Third Law of Motion).
Question:5 Question: Why is standing in boats or double decker buses not allowed, particularly in the upper deck of buses?
Answer: On tilting the centre of gravity of the boat or bus is lowered and it is likely to overturn.
Question:6. Question: Why is it recommended to add salt to water while boiling dal?
Answer:By addition of salt, the boiled point of water gets raised which helps in cooking the dal sooner.
Question:7. Question: Why is it the boiling point of sea water more than that of pure water?
Answer: Sea water contains salt, and other impurities which cause an elevation in its boiling point.
Question:8. Question: Why is it easier to spray water to which soap is added?
Answer: Addition of soap decreases the surface tension of water. The energy for spraying is directly proportional to surface tension.
Question:9. Question: Which is more elastic, rubber or steel?
Answer: Steel is more elastic for the same stress produced compared with rubber.
Question:10. Question: Why is the sky blue?
Answer: Violet and blue light have short waves which are scattered more than red light waves. While red light goes almost straight through the atmosphere, blue and violet light are scattered by particles in the atmosphere. Thus, we see a blue sky.
Question:11. Question: Why Does ink leak out of partially filled pen when taken to a higher altitude?
Answer: As we go up, the pressure and density of air goes on decreasing. A Partially filled pen leaks when taken to a higher altitude because the pressure of air acting on the ink inside the tube of the pen is greater than the pressure of the air outside.
Question:12. Question: On the moon, will the weight of a man be less or more than his weight on the earth?
Answer: The gravity of the moon is one-sixth that of the earth; hence the weight of a person on the surface of the moon will be one-sixth of his actual weight on earth.
Question:13. Question: Why do some liquid burn while others do not?
Answer:A liquid burns if its molecules can combine with oxygen in the air with the production of heat. Hence, oil burns but water does not.
Question:14. Question: Why can we see ourselves in a mirror?
Answer: We see objects when light rays from them reach our eyes. As mirrors have a shiny surface, the light rays are reflected back to us and enter our eyes.
Question:15. Question: Why does a solid chunk of iron sink in water but float in mercury?
Answer: Because the density of iron is more than that of water bus less than that of mercury.
Question:16. Question: Why is cooking quicker in a pressure cooker?
Answer: As the pressure inside the cooker increases, the boiling point of water is raised, hence, the cooking process is quicker.
Question:17. Question: When wood burns it crackles. Explain?
Answer: Wood contains a complex mixture of gases and tar forming vapors trapped under its surface. These gases and tar vapors escape, making a cracking sound.
Question:18. Question: Why do stars twinkle?
Answer: The light from a star reaches us after refraction as it passes through various layers of air. When the light passes through the earth?s atmosphere, it is made to flicker by the hot and cold ripples of air and it appears as if the stars are twinkling.
Question:19. Question: Why is it easier to roll a barrel than to pull it?
Answer: Because the rolling force of friction is less than the dynamic force of sliding friction.
Question:20. Question: If a feather, a wooden ball and a steel ball fall simultaneously in a vacuum, which one of these would fall faster?
Answer:All will fall at the same speed in vacuum because there will be no air resistance and the earth?s gravity will exert a similar gravitational pull on all.
Question:21. Question: When a man fires a gun, he is pushed back slightly. Why?
Answer: As the bullet leaves the nozzle of the gun?s barrel with momentum in a forward direction, as per Newton's Third Law of Motion, the ejection imparts to the gun as equal momentum in a backward direction.
Question:22. Question: Ice wrapped in a blanket or saw dust does not melt quickly. Why?
Answer: Both wood and wool are bad conductors of heat. They do not permit heat rays to reach the ice easily.
Question:23. Question: Why do we perspire on a hot day?
Answer: When the body temperature rises, the sweat glands are stimulated to secrete perspiration. It is nature's way to keep the body cool. During the process of evaporation of sweat, body heat is taken away, thus giving a sense of coolness.
Question:24. Question: Why does ice float on water but sink in alcohol?
Answer: Because ice is lighter than water it floats on it. However, ice is heavier than alcohol and therefore it sinks in alcohol.
Question:25. Question: Why do we perspire before rains?
Answer: Before the rain falls, the atmosphere gets saturated with water vapors; as a result, the process of evaporation of sweat is delayed.
Question:26. Question: Why does a thermometer kept in boiling water show no change in reading after 1000C?
Answer: The boiling point of water is 1000C. Once water starts boiling at this temperature, thermometer records no change in temperature. The quantity of heat supplied is being utilized as latent heat of evaporation to convert the water at boiling point into vapour.
Question:27. Question: Why do we bring our hands close to the mouth while shouting across to someone far away?
Answer:By keeping hands close to mouth the sound is not allowed to spread (Phenomenon of diffraction of sound) in all direction, but is directed to a particular direction and becomes louder.
Question:28. Question: Why does a corked bottle filled with water burst if left out on a frosty night?
Answer: Because of low temperature the water inside the bottle freezes. On freezing it expands, thereby its volume increases and pressure is exerted on the walls.
Question:29. Question: Why is a small gap left at the joint between two rails?
Answer: To permit expansion of rails due to heat generated by friction of a moving train.
Question:30. Question: Why cannot a copper wire be used to make elements in electric heater?
Answer:Copper melts at 108.30C and forms a black powder on reacting with atmospheric oxygen. For heater elements a metal should have more resistance to produce heat.
Question:31. Question: Why are water or mercury droplets always round when dropped on a clean glass?
Answer: The surface of a liquid is the seat of a special force as a result of which molecules on the surface are bound together to form something like a stretched membrane. They tend to compress the molecules below to the smallest possible volume, which causes the drop to take a round shape as for a given mass he sphere has minimum volume.
Question:32. Question: Why does a balloon filled with hydrogen rise in the air?
Answer:Weight of hydrogen is less than the weight of air displaced by it. In balloons hydrogen is normally filled because it is lighter than air.
Question:33. Question: Why do we lean forward while climbing a hill?
Answer: In order to keeps the vertical line passing through our centre of gravity always between our feet, which is essential to attain equilibrium or stability.
Question:34. Question: Why does smoke curl up in the air?
Answer: Smoke contains hot gases which being lighter in weight, follows a curved path because of the eddy currents that are set up in the air.
Question:35. Question: Why does an electric bulb explode when it is broken?
Answer: The bulb encompasses partial vacuum and as it breaks, air rushes in causing a small explosion.
Question:36. Question: Why does a man fall forward when he jumps out of a running train or bus?
Answer: He is in motion while in the train or bus. When he jumps out, his feet comes to rest while touching the ground but his upper portion which is still in motion propels him forward.
Question:37. Question: Why does an ordinary glass tumbler crack when very hot tea or milk is poured in it?
Answer: When a hot liquid is poured into a tumbler, the inner layer of the tumbler gets heated, it expands before the outer layer and an unequal expansion of both layers causes the tumbler to crack.
Question:38. Question: Why is a compass used as an indicator of direction?
Answer: The magnetic needles of a compass under the influence f the earth?s magnetic field lie in a north-south direction. Hence, we can identify direction.
Question:39. Question: Why is water from a hand pump warm in winter and cold in summer?
Answer: In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
Question:41. Question: Why is a rainbow seen after a shower?
Answer: After a shower, the clouds containing water droplets act like a prism through which the white light is dispersed producing a spectrum.
Question:42. Question: Why does a swimming pool appear less deep than is actually is?
Answer: The rays of light coming from the bottom of the pool pass from a denser medium (water) to a rarer medium (air) and are refracted (bend away from the normal). When the rays return to the surface, they form an image of the bottom of the pool at a point, which is little above the real position.
Question:43. Question: Why is one?s breath visible in winter but not in summer?
Answer: In winter, water vapor contained in the breath condenses into small droplets, which become visible but in summer they are quickly evaporated and not seen.
Question:44. Question: Why doesn?t the electric filament in an electric bulb burn
Answer: Firstly, because is made of tungsten which has a very high melting point (34100C) whereas the temperature of the filament required to glow is only 2700oC. Secondly, oxygen is absent since the bulb is filled with an inert gas which does not help in burning.
Question:45. Question: Why does blotting paper absorb ink?
Answer: Blotting paper has fine pores, which act like capillaries. When a portion of blotting paper is brought in contact with ink, ink enters the pores due to surface tension (capillary action f liquids) and is absorbed.
Question:46. Question: Why does a small iron sink in water but a large ship float?
Answer: The weight of water displaced by an iron ball is less than its own weight, whereas water displaced by the immersed portion of a ship is equal to its weight (Archimedes? Principle).
Question:47. Question: Why does ice float on water?
Answer: The weight of the ice block is equal to the weight of the liquid displaced by the immersed portion of the ice.
Question:48. Question: Why does moisture gather outside a tumbler containing cold water?
Answer: The water vapour in the air condenses on cooling and appears as droplets of water.
Question:49. Question: Why does kerosene float on water?
Answer: Because the density of kerosene is less than that of water. For the same reason cream rises in milk and floats at the top.
Question:50. Question: Why is the water in an open pond cool even on a hot summer day?
Answer: As the water evaporates from the open surface of a pond, heat is taken away in the process, leaving the surface cool.

51. Question: Why is it less difficult to cook rice or potatoes at higher altitudes?
Answer: Atmospheric pressure at higher altitudes is low and boils water below 100⁰C. The boiling point of water is directly proportional to the pressure on its surface.

52. Question: Why is it difficult to breathe at higher altitudes?
Answer: Because of low air pressure at higher altitudes the quantity of air is less, and so that of oxygen.

53. Question: Why are winter nights and summer nights warmer during cloudy weather than when the sky is clear?
Answer: Clouds being bad conductors of heat do not permit radiation of heat from land to escape into the sky. As this heat remains in the atmosphere, the cloudy nights are warmer.

54. Question: Why is a metal tyre heated before it is fixed on wooden wheels?
Answer: On heating, the metal tyre expands by which its circumference also increases. This makes fixing the wheel easier and therefore cooling down shrinks it; thus fixing the tyre tightly.

55. Question: Why is it easier to swim in the sea than in a river?
Answer: The density of sea water is higher; hence the up thrust is more than that of river water.

56. Question: Who will possibly learn swimming faster-a fat person or a thin person?
Answer: The fat person displaces more water which will help him float much more freely compared to a thin person.

57. Question: Why is a flash of lightening seen before thunder?
Answer: Because light travels faster than sound, it reaches the earth before the sound of thunder.

58. Question: Why cannot a petrol fire be extinguished by water?
Answer: Water, which is heavier than petrol, slips down permitting the petrol to rise to the surface and continue to burn. Besides, the existing temperature is so high that the water poured on the fire evaporates even before it can extinguish the fire. The latter is true if a small quantity of water is poured.

59. Question: Why does water remain cold in an earthen pot?
Answer: There are pores in an earthen pot which allow water to percolate to the outer surface. Here evaporation of water takes place thereby producing a cooling effect.

60. Question: Why do we place a wet cloth on the forehead of a patient suffering from high temperature?
Answer: Because of body?s temperature, water evaporating from the wet cloth produces a cooling effect and brings the temperature down.

61. Question: When a needle is placed on a small piece of blotting paper which is place on the surface of clean water, the blotting paper sinks after a few minutes but the needle floats. However, in a soap solution the needle sinks. Why?
Answer: The surface tension of clean water being higher than that of a soap solution, it cans support the weight of a needle due to its surface tension. By addition of soap, the surface tension of water reduces, thereby resulting in the sinking of the needle.

62. Question: To prevent multiplication of mosquitoes, it is recommended to sprinkle oil in the ponds with stagnant water. Why?
Answer: Mosquitoes breed in stagnant water. The larvae of mosquitoes keep floating on the surface of water due to surface tension. However, when oil is sprinkled, the surface tension is lowered resulting in drowning and death of the larvae.

63. Question: Why does oil rise on a cloth tape of an oil lamp?
Answer: The pores in the cloth tape suck oil due to the capillary action of oil.

64. Question: Why are ventilators in a room always made near the roof?
Answer: The hot air being lighter in weight tends to rise above and escape from the ventilators at the top. This allows the cool air to come in the room to take its place.

65. Question: How does ink get filled in a fountain pen?
Answer: When the rubber tube of a fountain pen immersed in ink is pressed, the air inside the tube comes out and when the pressure is released the ink rushes in to fill the air space in the tube.

66. Question: Why are air coolers less effective during the rainy season?
Answer: During the rainy reason, the atmosphere air is saturated with moisture. Therefore, the process of evaporation of water from the moist pads of the cooler slows down thereby not cooling the air blown out from the cooler.

67. Question: Why does grass gather more dew in nights than metallic objects such as stones?
Answer: Grass being a good radiator enables water vapour in the air to condense on it. Moreover, grass gives out water constantly (transpiration) which appears in the form of dew because the air near grass is saturated with water vapour and slows evaporation. Dew is formed on objects which are good radiations and bad conductors.

68. Question: If a lighted paper is introduced in a jar of carbon dioxide, its flame extinguishes. Why?
Answer: Because carbon dioxide does not help in burning. For burning, oxygen is required.

69. Question: Why does the mass of an iron increase on rusting?
Answer: Because rust is hydrated ferric oxide which adds to the mass of the iron rod. The process of rusting involves addition of hydrogen and oxygen elements to iron.

70. Question: Why does milk curdle?
Answer: Lactose (milk sugar) content of milk undergoes fermentation and changes into lactic acid which on reacting with milk protein (casein) form curd.

71. Question: Why does hard water not lather soap profusely?
Answer: Hard water contains sulphates and chlorides of magnesium and calcium which forms an insoluble compound with soap. Therefore, soap does not lather with hard water.

72. Question: Why is it dangerous to have charcoal fire burning in a closed room?
Answer: When charcoal burns it produces carbon monoxide which is suffocating and can cause death.

73. Question: Why is it dangerous to sleep under trees at night?
Answer: Plants respire at night and give out carbon dioxide which reduces the oxygen content of air required for breathing.

74. Question: Why does ENO's salt effervesce on addition of water?
Answer: It contains tartaric acid and sodium bicarbonate. On adding water, carbon dioxide is produced which when released into water causes effervescence.

75. Question: Why does milk turn sour?
Answer: The microbes react with milk and grow. They turn lactose into lactic acid which is sour in taste.