physics : class11 Cohesive Forces : Surface Tension : Properties of Bulk Matter MCQ Questions and Answers
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Cohesive Forces
MCQ questions and answers.
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MCQ Questions
1. What are cohesive forces?
A.
Forces of attraction between molecules of the same substance
B.
Forces of repulsion between molecules of different substances
C.
Forces between an object and the Earth
D.
Forces that act only on charged particles
Correct Answer:
Forces of attraction between molecules of the same substance
Explanation:
Cohesive forces are attractive forces acting between molecules of the same substance, such as water molecules attracting one another.
2. Which force helps water molecules remain together in a drop of water?
A.
Cohesive force
B.
Gravitational force only
C.
Magnetic force
D.
Nuclear force
Correct Answer:
Cohesive force
Explanation:
Cohesive attraction between water molecules holds the molecules together and helps form a water drop.
3. The nearly spherical shape of a small liquid drop is mainly due to cohesive forces and the tendency to
A.
Minimize its surface area
B.
Increase its temperature
C.
Increase its mass
D.
Lose all its molecules
Correct Answer:
Minimize its surface area
Explanation:
Cohesive forces cause a liquid surface to contract, so a small drop tends to take a spherical shape, which has the least surface area for a given volume.
4. In a liquid, a molecule well inside the liquid is attracted by cohesive forces
A.
Almost equally in all directions
B.
Only upward
C.
Only toward the surface
D.
Only toward the bottom
Correct Answer:
Almost equally in all directions
Explanation:
A molecule inside a liquid is surrounded by similar molecules, so cohesive attractions act nearly equally in all directions and produce nearly zero net force.
5. Why does a liquid surface behave like a stretched elastic film?
A.
Cohesive forces pull surface molecules toward the liquid
B.
Surface molecules have no attractive forces
C.
The liquid contains only gas molecules
D.
Cohesive forces act only on the container
Correct Answer:
Cohesive forces pull surface molecules toward the liquid
Explanation:
Surface molecules experience a net inward cohesive attraction from molecules below and beside them, making the surface tend to contract like a stretched film.
6. Which statement about cohesive forces in a liquid is correct?
A.
They act between molecules of the same liquid
B.
They act only between a liquid and a solid
C.
They are always repulsive
D.
They act only on electrically charged liquids
Correct Answer:
They act between molecules of the same liquid
Explanation:
Cohesive forces are attractions between similar molecules, such as the attraction between two molecules of water.
7. A liquid tends to reduce its exposed surface because of
A.
Cohesive attraction between its molecules
B.
The absence of molecular motion
C.
Repulsion from the surrounding air only
D.
The magnetic field of the Earth
Correct Answer:
Cohesive attraction between its molecules
Explanation:
Cohesive forces pull liquid molecules together and make the surface contract, reducing the exposed surface area.
8. If cohesive forces in a liquid become stronger, its surface tension generally
A.
Increases
B.
Becomes zero
C.
Always decreases
D.
Remains unrelated to molecular attraction
Correct Answer:
Increases
Explanation:
Stronger cohesive attraction makes the liquid surface more resistant to being stretched, resulting in greater surface tension.
9. Which example best demonstrates cohesion?
A.
Two water drops joining to form one larger drop
B.
A stone falling to the ground
C.
Iron being attracted by a magnet
D.
A balloon becoming charged by rubbing
Correct Answer:
Two water drops joining to form one larger drop
Explanation:
Water drops join because cohesive forces attract water molecules toward one another.
10. The inward pull experienced by a molecule at the surface of a liquid is mainly caused by
A.
Cohesive attraction from neighboring liquid molecules
B.
Repulsion from molecules inside the liquid
C.
Attraction from the Earth's core only
D.
The absence of molecules around it
Correct Answer:
Cohesive attraction from neighboring liquid molecules
Explanation:
A surface molecule has fewer liquid molecules above it, so cohesive attractions from neighboring molecules produce a net inward pull.
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