Surface Tension Test

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Surface Tension Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

The radius of a soap bubble is increased from R to 2 R. Work done in this process (T = surface tension) is

A
24 πR²T

B
48 πR²T

C
12 πR²T

D
36 πR²T

Solution
Question 2
1 / -0

A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then

A
Energy = 4VT (1/r − 1/R) is released

B
Energy = 3VT (1/r + 1/R) is released

C
Energy = 3VT (1/r − 1/R) is released

D
Energy is neither released nor absorbed

Solution

If the surface area changes, it will change the surface energy as well. As the surface area is decreasing, energy will be released.

Change in surface energy = T×ΔA

If there is n no. if small drops;Volume of a large drop=volume of n small drops
Question 3
1 / -0

At which of the following temperatures, the value of surface tension of water is minimum ?

A
4°C

B
25°C

C
50°C

D
75°C

Solution

Surface tension decreases with increase in temperature.
Question 4
1 / -0

If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because

A
Angle of contact is acute

B
Cohesion force is more

C
Adhesion force is more

D
The density of mercury is more

Solution

Cohesive force is the intermolecular attraction between like molecules, whereas adhesive force is the intermolecular force between unlike molecules. In the given case cohesive force between mercury molecules is more than adhesive force between mercury molecules and glass rod, hence mercury does not stick to rod.
Question 5
1 / -0

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 90^o

D
Cohesive force is equal to adhesive force

Solution

The glass rod is not wet when dipped in mercury because; the cohesive force of mercury molecules is more than the adhesive force between glass and mercury molecules
Question 6
1 / -0

Surface tension of a liquid is found to be influenced by

A
it increases with the increases with increase of temperature

B
nature of the liquid in contact

C
presence of soap that increases it

D
its variation with the concentration of the liquid

Solution

Surface tension of a liquid is found to be influenced by its variation with the concentration of the liquid.
Question 7
1 / -0

When a drop of water is dropped on oil surface, then :

A
It will mix up with oil

B
It spreads in the form of a film

C
It will deform

D
It remains spherical

Solution

When a water drop falls on the surface of oil, 2 forces come into play. 1 being the cohesion forces within the water molecules and the other being the adhesion forces between oil and water.

Now, as we all know that oil is hydrophobic in nature, as a result the adhesive forces between oil and water are much weaker compared to the cohesive forces between water and water.

Therefore, the water drop has a tendency to maintain its spherical shape in order to minimize the surface energy.
Question 8
1 / -0

Small liquid drops assume spherical shape because

A
Atmospheric pressure exerts a force on a liquid drop

B
Volume of a spherical drop is minimum

C
Gravitational force acts upon the drop

D
Liquid tends to have the minimum surface area due to surface tension

Solution

Sphere has the minimum surface area for the given volume of the liquid.
Question 9
1 / -0

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

Solution

Surface tension of water decrease with rise in temperature
Question 10
1 / -0

The force required to separate two glass plates of area 10⁻²m² with a film of water 0.05 mm thick between them, is (Surface tension of water is 70×10⁻³ N/m)

A
28 N

B
14 N

C
50 N

D
38 N

Solution

Force required to separate the plates

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Surface Tension Test - 3

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Surface Tension Test - 3

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SHARING IS CARING

Question 1

24 πR2T

48 πR2T

12 πR2T

36 πR2T

Solution

Question 2

Energy = 4VT (1/r − 1/R) is released

Energy = 3VT (1/r + 1/R) is released

Energy = 3VT (1/r − 1/R) is released

Energy is neither released nor absorbed

Solution

Question 3

4°C

25°C

50°C

75°C

Solution

Question 4

Angle of contact is acute

Cohesion force is more

Adhesion force is more

The density of mercury is more

Solution

Question 5

Cohesive force is less than adhesive force

Cohesive force is greater than adhesive force

Angle of contact is less than 90o

Cohesive force is equal to adhesive force

Solution

Question 6

it increases with the increases with increase of temperature

nature of the liquid in contact

presence of soap that increases it

its variation with the concentration of the liquid

Solution

Question 7

It will mix up with oil

It spreads in the form of a film

It will deform

It remains spherical

Solution

Question 8

Atmospheric pressure exerts a force on a liquid drop

Volume of a spherical drop is minimum

Gravitational force acts upon the drop

Liquid tends to have the minimum surface area due to surface tension

Solution

Question 9

Surface tension is more

Surface tension is less

Consumes less soap

None of these

Solution

Question 10

28 N

14 N

50 N

38 N

Solution

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24 πR²T

48 πR²T

12 πR²T

36 πR²T

Angle of contact is less than 90^o