1. What are cohesive forces?
A.
Attractive forces between molecules of the same substance
B.
Attractive forces between different substances
C.
Repulsive forces between molecules of the same substance
D.
Forces between a liquid and a solid surface
Correct Answer:
Attractive forces between molecules of the same substance
Explanation:
Cohesive forces are the attractive intermolecular forces acting between molecules of the same substance.
2. Which force helps hold the molecules of a liquid together?
A.
Cohesive force
B.
Nuclear force
C.
Magnetic force only
D.
Electrical repulsion
Correct Answer:
Cohesive force
Explanation:
Cohesive forces attract neighboring molecules of the same liquid and help keep the liquid together.
3. Surface tension of a liquid is mainly caused by cohesive forces acting on its:
A.
Surface molecules
B.
Container molecules
C.
Dissolved gas molecules only
D.
Solid impurities only
Correct Answer:
Surface molecules
Explanation:
Cohesive attraction among surface molecules produces a net inward force, leading to surface tension.
4. A liquid tends to form nearly spherical small droplets because of:
A.
Cohesive forces minimizing the surface area
B.
Repulsion between all liquid molecules
C.
The absence of intermolecular forces
D.
The freezing of the liquid surface
Correct Answer:
Cohesive forces minimizing the surface area
Explanation:
Cohesive forces pull liquid molecules together, and a sphere provides the smallest surface area for a given volume.
5. 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 its container
C.
They always push liquid molecules apart
D.
They exist only in gases
Correct Answer:
They act between molecules of the same liquid
Explanation:
Cohesive forces are attractions between similar molecules, such as water molecules attracting other water molecules.
6. If cohesive forces in a liquid become stronger, its surface tension generally:
A.
Increases
B.
Decreases to zero
C.
Remains impossible to measure
D.
Changes into a gas pressure
Correct Answer:
Increases
Explanation:
Stronger cohesion produces a stronger inward attraction among surface molecules, increasing surface tension.
7. The tendency of mercury to form rounded drops is mainly related to its:
A.
Strong cohesive forces
B.
Absence of intermolecular attraction
C.
Weak nuclear forces
D.
Complete lack of surface tension
Correct Answer:
Strong cohesive forces
Explanation:
Strong cohesive attraction between mercury atoms causes mercury to contract into rounded drops.
8. Within the bulk of a liquid, a molecule is attracted by cohesive forces from:
A.
Molecules surrounding it in different directions
B.
Only molecules above it
C.
Only the container wall
D.
No neighboring molecules
Correct Answer:
Molecules surrounding it in different directions
Explanation:
A molecule inside a liquid is surrounded by similar molecules, so cohesive attractions act around it in many directions.
9. Why does a liquid surface behave somewhat like a stretched film?
A.
Cohesive forces pull surface molecules inward
B.
Gas molecules permanently freeze at the surface
C.
Liquid molecules lose all attraction at the surface
D.
The liquid surface contains no molecules
Correct Answer:
Cohesive forces pull surface molecules inward
Explanation:
The inward pull caused by cohesive forces makes the liquid surface behave like a tense or stretched film.
10. Which example best shows the effect of cohesive forces?
A.
Water molecules sticking together to form a droplet
B.
A gas expanding to fill a container
C.
A solid conducting electricity
D.
A liquid changing color when heated
Correct Answer:
Water molecules sticking together to form a droplet
Explanation:
Water molecules attract one another through cohesive forces, allowing them to remain together as a droplet.
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