physics : class11 Surface Molecules and Cohesive Forces : Surface Energy : Properties of Bulk Matter MCQ Questions and Answers
Practice important
Surface Molecules and Cohesive Forces
MCQ questions and answers.
Page 1
of
1
|
10
MCQ Questions
1. A molecule inside a liquid is attracted by surrounding molecules in which manner?
A.
Equally in all directions
B.
Only upward
C.
Only downward
D.
Only toward the surface
Correct Answer:
Equally in all directions
Explanation:
A molecule inside the liquid is surrounded by similar molecules on all sides, so cohesive forces act equally in all directions and their resultant is zero.
2. What is the net cohesive force on a molecule situated at the free surface of a liquid?
A.
Zero in every direction
B.
Directed inward toward the liquid
C.
Directed vertically upward
D.
Directed horizontally outward
Correct Answer:
Directed inward toward the liquid
Explanation:
A surface molecule has fewer neighboring molecules above it, so the cohesive forces are unbalanced and the resultant force acts inward toward the liquid.
3. Why do molecules at the surface of a liquid possess more energy than molecules inside the liquid?
A.
They move faster than all internal molecules
B.
They experience unbalanced cohesive forces
C.
They have no mass
D.
They are repelled by all nearby molecules
Correct Answer:
They experience unbalanced cohesive forces
Explanation:
Surface molecules have fewer neighboring molecules and therefore experience unbalanced cohesive forces, giving them greater potential energy than molecules in the bulk.
4. The attractive force between molecules of the same substance is called:
A.
Adhesive force
B.
Gravitational force
C.
Cohesive force
D.
Magnetic force
Correct Answer:
Cohesive force
Explanation:
Cohesive force is the force of attraction between molecules of the same substance, such as molecules within a liquid.
5. In a liquid, cohesive forces mainly act between:
A.
The liquid molecules themselves
B.
The liquid and the container only
C.
The liquid and Earth only
D.
Light waves and liquid molecules
Correct Answer:
The liquid molecules themselves
Explanation:
Cohesive forces are intermolecular attractive forces between molecules of the same liquid.
6. What happens to a liquid molecule when it is moved from the interior to the surface?
A.
Its surface potential energy increases
B.
Its mass becomes zero
C.
Its cohesive force becomes completely absent
D.
Its temperature must become zero
Correct Answer:
Its surface potential energy increases
Explanation:
Moving a molecule to the surface requires work against cohesive forces, so its surface potential energy increases.
7. Why does a liquid tend to have the smallest possible surface area?
A.
Surface molecules have no cohesive forces
B.
The liquid tends to reduce its surface energy
C.
Internal molecules push all surface molecules outward
D.
The liquid has maximum energy at minimum area
Correct Answer:
The liquid tends to reduce its surface energy
Explanation:
Surface molecules possess excess energy, so a liquid tends to reduce its surface area to minimize the number of surface molecules and hence its surface energy.
8. Which statement correctly compares a molecule inside a liquid with one at its surface?
A.
Both experience zero cohesive force
B.
The internal molecule has balanced forces, while the surface molecule has unbalanced forces
C.
The surface molecule has balanced forces, while the internal molecule has unbalanced forces
D.
Both experience only outward cohesive forces
Correct Answer:
The internal molecule has balanced forces, while the surface molecule has unbalanced forces
Explanation:
An internal molecule is attracted equally in all directions, whereas a surface molecule has a net inward cohesive force because neighboring molecules are missing above it.
9. What work is required to bring a molecule from the interior of a liquid to its surface?
A.
Work against cohesive attraction
B.
Work against nuclear attraction
C.
Work against light pressure only
D.
No work under any condition
Correct Answer:
Work against cohesive attraction
Explanation:
A molecule is attracted toward surrounding molecules in the liquid, so work must be done against cohesive forces to move it to the surface.
10. The excess energy possessed by molecules at the free surface of a liquid is known as:
A.
Surface energy
B.
Sound energy
C.
Nuclear energy
D.
Electrical energy
Correct Answer:
Surface energy
Explanation:
Surface energy is the excess energy of surface molecules arising from their unbalanced cohesive forces compared with molecules inside the liquid.
Short Questions and Answers
Practice short questions and answers related to
Surface Molecules and Cohesive Forces
.
Short questions are currently unavailable for this page.