# Surface Tension Questions and Answers ### Surface Tension: Questions, MCQs:

Ques: Surface tension may be defined as
(a) The work done per unit area in increasing the surface area of a liquid under isothermal condition
(b) The work done per unit area in increasing the surface area of a liquid under adiabatic condition
(c) The work done per unit area in increasing the surface area of a liquid under both isothermal and adiabatic conditions
(d) Free surface energy per unit volume

Ans. (a)

Ques: A wooden stick 2m long is floating on the surface of water. The surface tension of water 0.07 N/m. By putting soap solution on one side of the sticks the surface tension is reduced to 0.06 N/m. The net force on the stick will be
(a) 0.07 N
(b) 0.06 N
(c) 0.01 N
(d) 0.02 N

Ans. (d)

Ques: Consider a liquid contained in a vessel. The liquid solid  adhesive force is very weak as compared to the cohesive force in the liquid. The shape of the liquid surface near the solid shall be
(a)

Horizontal
(b) Almost vertical
(c) Concave
(d) Convex

Ans. (d)

Ques: Oil spreads over the surface of water whereas water does not spread over the surface of the oil, due to
(a) Surface tension of water is very high
(b) Surface tension of water is very low
(c) Viscosity of oil is high
(d) Viscosity of water is high

Ans. (a)

Ques: Mercury does not wet glass, wood or iron because
(a) Cohesive force is less than adhesive force
(b) Cohesive force is greater than adhesive force
(c) Angle of contact is less than 90o
(d) Cohesive force is equal to adhesive force

Ans. (b)

Ques: It is easy to wash clothes in hot water because its
(a) Surface tension is more
(b) Surface tension is less
(c) Consumes less soap
(d) None of these

Ans. (b)

Ques: On mixing the salt in water, the surface tension of water will
(a) Increase
(b) Decrease
(c) Remain unchanged
(d) None of the above

Ans. (a)

Ques: The property of surface tension is obtained in
(a) Solids, liquids and gases
(b) Liquids
(c) Gases
(d) Matter

Ans. (b)

Ques: Which of the fact is not due to surface tension
(a) Dancing of a camphor piece over the surface of water
(b) Small mercury drop itself becomes spherical
(c) A liquid surface comes at rest after stirring
(d) Mercury does not wet the glass vessel

Ans. (c)

Ques: Two pieces of glass plate one upon the other with a little water in between them cannot be separated easily because of
(a) Inertia
(b)  Pressure
(c) Surface tension
(d)  Viscosity

Ans. (c)

Ques: The temperature at which the surface tension of water is zero
(a) 0°C
(b) 277 K
(c) 370°C
(d) Slightly less than 647 K

Ans. (c)
(d)

Ques: Water does not wet an oily glass because
(a) Cohesive force of oil > adhesive force between oil and glass
(b) Cohesive force of oil > cohesive force of water
(c) Oil repels water
(d) Cohesive force for water > adhesive force between water and oil molecules

Ans. (d)

Ques: Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid because
(a) Force of surface tension is equal and opposite to the force of gravity
(b) Force of surface tension predominates the force of gravity
(c) Force of gravity predominates the force of surface tension
(d) Force of gravity and force of surface tension act in the same direction and are equal

Ans. (b)

Related: physics Kinematics test

Ques: The spherical shape of rain-drop is due to
(a) Density of the liquid
(b) Surface tension
(c) Atmospheric pressure
(d) Gravity

Ans. (b)

Ques: When there is no external force, the shape of a liquid drop is determined by
(a) Surface tension of the liquid
(b) Density of liquid
(c) Viscosity of liquid
(d) Temperature of air only

Ans. (a)

Ques: Coatings used on raincoat are waterproof because
(a) Water is absorbed by the coating
(b) Cohesive force becomes greater
(c) Water is not scattered away by the coating
(d) Angle of contact decreases

Ans. (b)