1. Surface tension is caused by
A) Cohesive forces
B) Adhesive forces
C) Friction
D) Gravity
Answer: A) Cohesive forces
Explanation: Molecules at the surface experience an inward pull due to cohesive forces, creating surface tension.
2. Surface tension acts
A) Tangentially to the surface
B) Perpendicular to the surface
C) Vertically upward
D) Randomly
Answer: A) Tangentially to the surface
Explanation: The force acts along the surface, trying to minimize the area.
3. The SI unit of surface tension is
A) Newton per meter
B) Newton per square meter
C) Joule
D) Pascal
Answer: A) Newton per meter
Explanation: It measures the force per unit length along the surface.
4. Surface tension of a liquid decreases with
A) Increase in temperature
B) Decrease in temperature
C) Increase in pressure
D) Decrease in pressure
Answer: A) Increase in temperature
Explanation: Heat reduces molecular attraction, thus reducing surface tension.
5. The shape of a liquid drop is spherical because
A) Gravity
B) Viscosity
C) Surface tension
D) Adhesion
Answer: C) Surface tension
Explanation: A sphere has the smallest surface area for a given volume.
6. Surface tension is a property of
A) Liquids
B) Solids
C) Gases
D) All states of matter
Answer: A) Liquids
Explanation: It occurs at the liquid-air interface due to molecular attraction.
7. When detergent is added to water, its surface tension
A) Decreases
B) Increases
C) Remains same
D) Becomes zero
Answer: A) Decreases
Explanation: Detergent molecules reduce cohesive forces between water molecules.
8. The rise of liquid in a thin tube is due to
A) Surface tension
B) Viscosity
C) Density
D) Pressure difference
Answer: A) Surface tension
Explanation: Surface tension pulls the liquid along the tube walls causing capillary rise.
9. The meniscus of water in a glass tube is
A) Concave
B) Convex
C) Flat
D) Irregular
Answer: A) Concave
Explanation: Water wets glass, forming a concave surface.
10. The meniscus of mercury in a glass tube is
A) Convex
B) Concave
C) Flat
D) Horizontal
Answer: A) Convex
Explanation: Mercury does not wet glass, creating a convex surface.
11. Capillarity is the phenomenon due to
A) Surface tension
B) Density
C) Viscosity
D) Friction
Answer: A) Surface tension
Explanation: It causes the liquid to rise or fall in narrow tubes.
12. The liquid that does not wet the solid surface shows
A) Depression in capillary
B) Rise in capillary
C) Flat surface
D) Uniform height
Answer: A) Depression in capillary
Explanation: When cohesion dominates adhesion, the liquid level falls.
13. Soap solution has lower surface tension than water because
A) It contains surfactants
B) It contains salt
C) It contains alcohol
D) It has less density
Answer: A) It contains surfactants
Explanation: Surfactants reduce molecular attraction in the surface layer.
14. Mercury does not wet glass because
A) Cohesive forces are stronger than adhesive forces
B) Adhesive forces are stronger
C) Gravity acts downward
D) Mercury is a metal
Answer: A) Cohesive forces are stronger than adhesive forces
15. Water wets glass because
A) Adhesive forces are stronger than cohesive forces
B) Cohesive forces are stronger
C) It is dense
D) Gravity helps
Answer: A) Adhesive forces are stronger
16. The insects walking on water are supported by
A) Surface tension
B) Buoyancy
C) Density
D) Friction
Answer: A) Surface tension
Explanation: The stretched surface layer of water supports light insects.
17. The property responsible for spherical soap bubbles is
A) Surface tension
B) Elasticity
C) Pressure
D) Viscosity
Answer: A) Surface tension
18. The addition of salt to water
A) Increases surface tension
B) Decreases surface tension
C) Has no effect
D) Destroys surface tension
Answer: A) Increases surface tension
Explanation: Salt strengthens intermolecular attraction.
19. Surface tension is maximum for
A) Mercury
B) Water
C) Alcohol
D) Kerosene
Answer: A) Mercury
Explanation: Metallic bonding gives mercury very strong cohesive forces.
20. A clean glass capillary shows
A) Rise of water
B) Fall of mercury
C) Both A and B
D) None
Answer: C) Both A and B
21. Capillary rise is more in
A) Narrow tube
B) Wide tube
C) Both same
D) Irregular tube
Answer: A) Narrow tube
Explanation: Narrower tubes have higher capillary action.
22. The energy associated with the surface of a liquid is called
A) Surface energy
B) Kinetic energy
C) Potential energy
D) Thermal energy
Answer: A) Surface energy
23. The surface tension of hot water is
A) Less than that of cold water
B) Greater than cold water
C) Equal
D) Zero
Answer: A) Less than that of cold water
24. Surface tension depends on
A) Nature of liquid
B) Temperature
C) Impurities
D) All of these
Answer: D) All of these
25. The work done to increase the surface area of a liquid is stored as
A) Surface energy
B) Heat energy
C) Kinetic energy
D) Gravitational energy
Answer: A) Surface energy
26. Soap helps in cleaning because it
A) Lowers surface tension of water
B) Increases surface tension
C) Makes water hard
D) Removes cohesion
Answer: A) Lowers surface tension of water
27. The phenomenon of surface tension is absent in
A) Solids
B) Liquids
C) Gases
D) Vacuum
Answer: D) Vacuum
Explanation: No molecules exist in vacuum to create tension.
28. Surface tension tries to
A) Decrease the surface area of a liquid
B) Increase the surface area
C) Keep area constant
D) Remove pressure
Answer: A) Decrease the surface area
29. When small droplets combine to form a big drop,
A) Surface energy decreases
B) Surface energy increases
C) Energy remains constant
D) Pressure increases
Answer: A) Surface energy decreases
30. At the critical temperature of a liquid, surface tension
A) Becomes zero
B) Becomes maximum
C) Remains constant
D) Doubles
Answer: A) Becomes zero
31. Capillary rise stops when
A) Weight of liquid balances upward surface force
B) Tube is filled
C) Pressure equals zero
D) Liquid evaporates
Answer: A) Weight of liquid balances upward surface force
32. The surface of a liquid behaves like
A) A stretched elastic membrane
B) A solid wall
C) A porous sheet
D) A rough layer
Answer: A) A stretched elastic membrane
33. Surface tension is responsible for
A) Formation of raindrops
B) Floating of needle on water
C) Capillary rise
D) All of these
Answer: D) All of these
34. The floating of camphor pieces on water is due to
A) Surface tension
B) Density
C) Adhesion
D) Capillarity
Answer: A) Surface tension
35. Detergents clean better in
A) Hot water
B) Cold water
C) Both same
D) Ice water
Answer: A) Hot water
Explanation: Heat lowers surface tension, making detergent more effective.
36. Surface tension is not affected much by
A) Normal pressure changes
B) Temperature
C) Impurities
D) Chemical nature
Answer: A) Normal pressure changes
37. The property responsible for formation of soap bubbles is
A) Surface tension
B) Elasticity
C) Density
D) Viscosity
Answer: A) Surface tension
38. When oil spreads on water, it forms a thin film because
A) Its surface tension is lower
B) It is lighter
C) It mixes with water
D) It evaporates
Answer: A) Its surface tension is lower
39. Surface tension is measured using
A) Capillary rise method
B) Drop method
C) Ring method
D) All of these
Answer: D) All of these
40. The contact angle for water and glass is
A) Small or zero
B) Ninety degrees
C) Large
D) Undefined
Answer: A) Small or zero
41. The pressure inside a soap bubble is
A) Greater than outside pressure
B) Equal to outside pressure
C) Less than outside pressure
D) Same as atmosphere
Answer: A) Greater than outside pressure
Explanation: Surface tension compresses the air inside, increasing its pressure.
42. When the radius of a bubble decreases, the pressure inside
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
Answer: A) Increases
Explanation: Smaller bubbles have more curvature, so surface tension makes the internal pressure higher.
43. When a soap bubble bursts,
A) The air inside escapes
B) The bubble collapses
C) Surface energy is released
D) All of these
Answer: D) All of these
44. The temperature at which the surface tension becomes zero is called
A) Critical temperature
B) Boiling point
C) Melting point
D) Triple point
Answer: A) Critical temperature
Explanation: At this point, liquid and vapor become indistinguishable.
45. The rise of a liquid in a capillary tube is due to
A) Surface tension and adhesion
B) Gravity
C) Viscosity
D) Elasticity
Answer: A) Surface tension and adhesion
46. When water is cooled, its surface tension
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero
Answer: A) Increases
Explanation: Lower temperature strengthens molecular attraction.
47. Surface tension of liquids is generally
A) Greater for pure liquids
B) Greater for impure liquids
C) Independent of purity
D) Random
Answer: A) Greater for pure liquids
48. If the surface area of a liquid increases, its potential energy
A) Increases
B) Decreases
C) Remains same
D) Becomes zero
Answer: A) Increases
Explanation: Larger surface area means more surface molecules and higher energy.
49. When a needle floats on water, it is due to
A) Surface tension
B) Density difference
C) Buoyancy
D) Adhesion
Answer: A) Surface tension
50. Liquids which wet solids have
A) Stronger adhesive forces than cohesive forces
B) Stronger cohesive forces
C) Equal forces
D) No molecular forces
Answer: A) Stronger adhesive forces than cohesive forces
51. Surface tension is not observed in
A) Gases
B) Solids
C) Liquids
D) Plasma
Answer: A) Gases
Explanation: Gas molecules are far apart, so cohesive forces are negligible.
52. The liquid which shows capillary depression is
A) Mercury
B) Water
C) Alcohol
D) Milk
Answer: A) Mercury
Explanation: Mercury does not wet glass; its level falls.
53. The meniscus of mercury in glass is
A) Convex
B) Concave
C) Flat
D) Irregular
Answer: A) Convex
54. The meniscus of water in glass is
A) Concave
B) Convex
C) Flat
D) Circular
Answer: A) Concave
55. Surface tension acts
A) Along the surface of the liquid
B) Normal to the surface
C) Vertically downward
D) Upward
Answer: A) Along the surface of the liquid
56. Surface tension is maximum in
A) Mercury
B) Alcohol
C) Kerosene
D) Water
Answer: A) Mercury
57. Capillary rise or fall depends on
A) Surface tension and adhesive forces
B) Density of air
C) Volume of liquid
D) Mass of liquid
Answer: A) Surface tension and adhesive forces
58. Surface tension decreases when
A) Temperature rises
B) Impurities are added
C) Soap is mixed
D) All of these
Answer: D) All of these
59. A detergent acts as a
A) Surface tension reducing agent
B) Surface tension increasing agent
C) Neutral agent
D) Solidifier
Answer: A) Surface tension reducing agent
60. The floating of camphor pieces on water surface is due to
A) Surface tension variation
B) Buoyancy
C) Density
D) Cohesion
Answer: A) Surface tension variation
61. Oil spreads over water because
A) Oil has less surface tension than water
B) Oil is heavier
C) Oil dissolves in water
D) Oil repels water
Answer: A) Oil has less surface tension than water
62. The shape of a free soap bubble is
A) Spherical
B) Elliptical
C) Cylindrical
D) Irregular
Answer: A) Spherical
Explanation: Surface tension makes the bubble’s surface area minimum.
63. When two soap bubbles join, the new bubble has
A) Larger radius
B) Smaller radius
C) Same radius
D) No definite shape
Answer: A) Larger radius
64. The rise of water in a glass tube shows that
A) Water wets glass
B) Water does not wet glass
C) Mercury wets glass
D) Surface tension is zero
Answer: A) Water wets glass
65. If the radius of a capillary tube is reduced, the rise of liquid
A) Increases
B) Decreases
C) Remains constant
D) Stops
Answer: A) Increases
66. The value of surface tension for water is approximately
A) High
B) Medium
C) Low
D) Very low
Answer: A) High
67. When impurities are added to a liquid, its surface tension
A) May increase or decrease
B) Always increases
C) Always decreases
D) Remains constant
Answer: A) May increase or decrease
68. Surface tension depends upon
A) Nature of liquid
B) Surrounding medium
C) Temperature
D) All of these
Answer: D) All of these
69. Surface energy and surface tension are
A) Numerically equal
B) Opposite in nature
C) Unrelated
D) Always different
Answer: A) Numerically equal
70. The spherical shape of raindrops is due to
A) Surface tension
B) Air resistance
C) Gravity
D) Pressure difference
Answer: A) Surface tension
71. The pressure inside small raindrops is
A) More than the outside
B) Less than outside
C) Same as outside
D) Equal to atmospheric
Answer: A) More than the outside
72. Surface tension of liquids is reduced by
A) Heating
B) Adding soap
C) Adding alcohol
D) All of these
Answer: D) All of these
73. The capillary action will be less if
A) Tube is wide
B) Tube is narrow
C) Adhesion is strong
D) Cohesion is weak
Answer: A) Tube is wide
74. When a liquid wets the surface of a solid, the angle of contact is
A) Acute
B) Right angle
C) Obtuse
D) Zero
Answer: A) Acute
75. The excess pressure inside a bubble depends on
A) Surface tension
B) Size of the bubble
C) Both A and B
D) None
Answer: C) Both A and B
76. Surface tension decreases sharply when
A) Detergent is added
B) Salt is added
C) Temperature falls
D) Pressure increases
Answer: A) Detergent is added
77. Which of the following liquids has least surface tension?
A) Alcohol
B) Water
C) Mercury
D) Kerosene
Answer: A) Alcohol
78. The rise of liquid in a capillary is greater if
A) Density of liquid is small
B) Tube is thinner
C) Adhesion is stronger
D) All of these
Answer: D) All of these
79. The angle of contact for mercury and glass is
A) Obtuse
B) Acute
C) Zero
D) Ninety degrees
Answer: A) Obtuse
80. The unit of surface tension can also be expressed as
A) Energy per unit area
B) Force per unit length
C) Both A and B
D) Pressure
Answer: C) Both A and B
81. Surface tension causes small drops of liquid to
A) Merge into a single larger drop
B) Repel each other
C) Spread widely
D) Evaporate faster
Answer: A) Merge into a single larger drop
82. The value of surface tension of water is greater than that of
A) Alcohol
B) Kerosene
C) Petrol
D) All of these
Answer: D) All of these
83. The rise of a liquid in a narrow tube is called
A) Capillary rise
B) Diffusion
C) Adhesion
D) Viscosity
Answer: A) Capillary rise
84. The depression of mercury in a glass tube is called
A) Capillary fall
B) Capillary rise
C) Surface fall
D) None
Answer: A) Capillary fall
85. When two drops combine to form one, the total energy
A) Decreases
B) Increases
C) Remains same
D) Becomes zero
Answer: A) Decreases
86. A soap bubble is lighter than air because
A) It contains air under low pressure
B) It is filled with vacuum
C) It floats by surface tension
D) It contains hydrogen
Answer: A) It contains air under low pressure
87. The work done in blowing a bubble appears as
A) Surface energy
B) Heat
C) Elastic energy
D) Sound
Answer: A) Surface energy
88. A liquid with high surface tension tends to
A) Form spherical drops
B) Spread easily
C) Evaporate quickly
D) Mix with others
Answer: A) Form spherical drops
89. A liquid wets a solid when
A) Adhesion exceeds cohesion
B) Cohesion exceeds adhesion
C) Both equal
D) Surface tension is high
Answer: A) Adhesion exceeds cohesion
90. A non-wetting liquid forms
A) Convex meniscus
B) Concave meniscus
C) Flat surface
D) Irregular surface
Answer: A) Convex meniscus
91. Surface tension is responsible for
A) Formation of soap bubbles
B) Rise of liquid in capillaries
C) Floating of insects on water
D) All of these
Answer: D) All of these
92. The property of liquids that resists external force on the surface is
A) Surface tension
B) Viscosity
C) Density
D) Elasticity
Answer: A) Surface tension
93. Surface tension acts only at
A) The surface layer
B) The bottom
C) The sides
D) Entire volume
Answer: A) The surface layer
94. The angle between the tangent to liquid surface and solid surface is called
A) Angle of contact
B) Angle of friction
C) Angle of cohesion
D) Angle of adhesion
Answer: A) Angle of contact
95. Surface tension tends to
A) Reduce surface area
B) Increase volume
C) Increase surface area
D) Reduce volume
Answer: A) Reduce surface area
96. The molecules at the surface of a liquid have
A) Higher potential energy
B) Lower potential energy
C) Equal energy
D) No energy
Answer: A) Higher potential energy
97. The unit of surface energy is same as that of
A) Surface tension
B) Energy
C) Pressure
D) Work
Answer: A) Surface tension
98. The cleaning power of soap solution depends on
A) Low surface tension
B) High viscosity
C) High surface tension
D) Density
Answer: A) Low surface tension
99. Surface tension helps in
A) Movement of water in plants
B) Formation of drops
C) Capillary action
D) All of these
Answer: D) All of these
100. The phenomenon of surface tension disappears when
A) The liquid boils
B) The liquid solidifies
C) Temperature reaches critical point
D) Pressure increases
Answer: C) Temperature reaches critical point