Surface Tension Test

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Surface Tension Test - 9

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Weekly Quiz Competition

Question 1
1 / -0

What is the excess pressure inside a bubble of soap solution of radius 5.00 mm, given that the surface tension of soap solution at the temperature (20° C20° C) is 2.50 × 10^–2 N/m?

A
10 Pa

B
20 Pa

C
1.06 × 10⁵ pa

D
15 Pa

Solution

Hint: The pressure difference between the inside pressure and outside pressure is called the excess pressure.

Step 1: Find the excess pressure.

The surface tension of soap bubble, S = 2.5×10⁻²

Radius, r = 5 × 10⁻³ m
Question 2
1 / -0

Two narrow bores of diameters 3.0 mm and 6.0 mm are joined together to form a U-tube open at both ends. If the U-tube contains water, what is the difference in its levels in the two limbs of the tube? The surface tension of water at the temperature of the experiment is 7.3 × 10^–2 N m^–1. Take the angle of contact to be zero and the density of water to be 1.0 × 10³ kg m^–3 (g = 9.8 m s^-2).

A
4.95 mm

B
3.73 mm

C
8.91 mm

D
5.36 mm

Solution

Hint: Equate the pressure in both limbs.
Question 3
1 / -0

Soap helps in cleaning clothes, because

A
It attracts the dirt particles

B
It decreases the surface tension of water

C
It increases the cohesive force between water molecules

D
It increases the angle of contact

Solution

Soap helps in cleaning clothes because it increases the surface tension of water.
Question 4
1 / -0

On increasing temperature of a liquid, its surface tension generally

A
Increases

B
Decreases

C
Remains constant

D
First increases and then decreases

Solution

On increasing of a liquid, its surface tension generally decreases.
Question 5
1 / -0

The raincoats are made water proof by coating it with a material, which

A
Absorb water

B
Increase surface tension of water

C
Increase the angle of contact

D
Decreases the density of water

Solution

The raincoats are made waterproof by coating it with a material which increases angle of contact.
Question 6
1 / -0

An iron needle slowly placed on the surface of water floats because

A
It displaces water more than its weight

B
The density of material of needle is less than that of water

C
Of surface tension

D
Of its shape

Solution

Surface tension is responsible for needle floating on surface of water when slowly placed.
Question 7
1 / -0

Two water droplets merge with each other to form a larger droplet. In this process

A
Energy is liberated

B
Energy is absorbed

C
Energy is neither liberated nor absorbed

D
Some mass is converted into energy

Solution

When two drops merge, their volume gets added but their total surface area decreases. Hence total surface energy decreases the remaining energy is liberated.
Question 8
1 / -0

The radius of a soap bubble is r. The surface tension of soap solution is 'S'. Keeping temperature constant, the radius of the soap bubble is soubled. The energy necessary for this will be

A
24 πr²S

B
8 πr²S

C
16 πr²S

D
12 πr²S

Solution

The energy required to change increase the size of the bubble.

T & S means surface tension.
Question 9
1 / -0

The surface tension of a liquid is 5 N/m. If a film is held on a ring of area 0.02 m², its surface energy is about

A
5×10⁻² J

B
2.5×10⁻²J

C
2×10⁻¹ J

D
3×10⁻¹ J

Solution

Since, there are two surfaces of equal area formed on a ring. The total surface energy of the film is given by

E = 2TA = 2 x 5 x 0.02J

= 0.2J = 2 x 10⁻¹J
Question 10
1 / -0

Two soap bubbles having radii 3 cm and 4 cm in vacuum, coalesce under isothermal conditions. The radius of the new bubble is

A
1 cm

B
5 cm

C
7 cm

D
3.5 cm

Solution

For isothermal conditions, Boyle's law holds good

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Surface Tension Test - 9

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Surface Tension Test - 9

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SHARING IS CARING

Question 1

10 Pa

20 Pa

1.06 × 105 pa

15 Pa

Solution

Question 2

4.95 mm

3.73 mm

8.91 mm

5.36 mm

Solution

Question 3

It attracts the dirt particles

It decreases the surface tension of water

It increases the cohesive force between water molecules

It increases the angle of contact

Solution

Question 4

Increases

Decreases

Remains constant

First increases and then decreases

Solution

Question 5

Absorb water

Increase surface tension of water

Increase the angle of contact

Decreases the density of water

Solution

Question 6

It displaces water more than its weight

The density of material of needle is less than that of water

Of surface tension

Of its shape

Solution

Question 7

Energy is liberated

Energy is absorbed

Energy is neither liberated nor absorbed

Some mass is converted into energy

Solution

Question 8

24 πr2S

8 πr2S

16 πr2S

12 πr2S

Solution

Question 9

5×10−2 J

2.5×10−2J

2×10−1 J

3×10−1 J

Solution

Question 10

1 cm

5 cm

7 cm

3.5 cm

Solution

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1.06 × 10⁵ pa

24 πr²S

8 πr²S

16 πr²S

12 πr²S

5×10⁻² J

2.5×10⁻²J

2×10⁻¹ J

3×10⁻¹ J