Surface energy and surface tension, angle of contact, excess pressure across curved surfaces - Question Bank

1. What is the effect of adding a detergent to water on its surface tension?
A) It increases the surface tension.
B) It decreases the surface tension.
C) It has no effect on surface tension.
D) It makes the surface tension zero.
2. A liquid exhibits positive excess pressure across its curved surface when the surface is:
A) Concave towards the gas phase.
B) Convex towards the gas phase.
C) Flat.
D) Irregularly shaped.
3. Which of the following correctly describes the relationship between surface tension (T), surface energy (E), and area (A)?
A) T = E/A
B) E = T*A
C) A = T*E
D) T = A/E
4. The work done to form a spherical soap bubble of radius R from a flat film is:
A) 2 * (4 * pi * R^2) * T
B) (4 * pi * R^2) * T
C) 8 * pi * R * T
D) 4 * pi * R * T
5. When a liquid rises in a capillary tube, the pressure just below the surface inside the tube is:
A) Equal to the atmospheric pressure.
B) Less than the atmospheric pressure.
C) Greater than the atmospheric pressure.
D) Zero.
6. If the radius of a capillary tube is halved, the rise of the liquid in the tube will be:
A) Halved
B) Doubled
C) Four times
D) Unchanged
7. The excess pressure in a soap bubble is twice that in a liquid drop of the same radius because:
A) Soap molecules increase surface tension.
B) A soap bubble has two free surfaces.
C) Soap bubbles are less stable.
D) The liquid inside the bubble is denser.
8. Which of the following statements about surface tension is INCORRECT?
A) It is the force per unit length acting along the surface.
B) It is the energy per unit area of the surface.
C) It is independent of temperature.
D) It is a phenomenon at the interface of liquid and gas/solid.
9. A clean glass plate is dipped in mercury and taken out. The surface of mercury on the glass plate will be:
A) Convex
B) Concave
C) Flat
D) Irregular
10. The angle of contact is measured between:
A) The tangent to the liquid surface and the solid surface.
B) The tangent to the liquid surface at the point of contact and the solid surface.
C) The normal to the liquid surface and the solid surface.
D) The tangent to the liquid surface and the normal to the solid surface.
11. If a small drop of liquid is broken into N identical smaller droplets, the total surface energy will:
A) Increase
B) Decrease
C) Remain unchanged
D) Become zero
12. The excess pressure inside a spherical bubble formed due to aeration in a liquid is given by:
A) 2T/R
B) 4T/R
C) T/R
D) 8T/R
13. A liquid rises to a height h in a capillary tube of radius r. If the surface tension is T and the angle of contact is theta, the weight of the liquid column is balanced by:
A) 2 * pi * r * T * cos(theta)
B) pi * r^2 * rho * g * h
C) 2 * pi * r * T
D) pi * r * T * sin(theta)
14. If the surface tension of water is 0.072 N/m, the work done to increase the surface area of a water film from 10 cm^2 to 100 cm^2 is:
A) 0.0063 J
B) 0.063 J
C) 0.63 J
D) 6.3 J
15. The excess pressure across a concave surface of a liquid is:
A) Positive (greater than outside pressure)
B) Negative (less than outside pressure)
C) Zero
D) Dependent on the density.
16. The excess pressure across a convex surface of a liquid is:
A) Positive (greater than outside pressure)
B) Negative (less than outside pressure)
C) Zero
D) Dependent on the volume.
17. When a liquid is in equilibrium in a container, the surface of the liquid adjusts itself to:
A) Maximize its surface area.
B) Minimize its surface area.
C) Maintain a constant surface area.
D) Be parallel to the gravitational force.
18. The force exerted by surface tension on a line of length L is:
A) T/L
B) T*L
C) T^2*L
D) T/(L^2)
19. Which factor does NOT affect the angle of contact?
A) Nature of the solid
B) Nature of the liquid
C) Presence of impurities
D) Temperature of the liquid
20. Surface tension is a property of:
A) Gases only
B) Liquids only
C) Solids only
D) Liquids and gases
21. If the radius of a soap bubble is doubled, the excess pressure inside it will:
A) Increase by a factor of 2
B) Decrease by a factor of 2
C) Increase by a factor of 4
D) Decrease by a factor of 4
22. The phenomenon of capillarity is a consequence of:
A) Surface tension and adhesive forces.
B) Surface tension and cohesive forces.
C) Surface tension and viscosity.
D) Surface tension and density.
23. The angle of contact for mercury in a glass tube is approximately:
A) 0 degrees
B) 30 degrees
C) 90 degrees
D) 140 degrees
24. Which of the following liquids has the highest surface tension at room temperature?
A) Water
B) Alcohol
C) Mercury
D) Kerosene
25. Excess pressure inside a bubble of radius R is proportional to:
A) R
B) R^2
C) 1/R
D) 1/R^2
26. If the angle of contact is 0 degrees, the liquid:
A) Forms a convex meniscus.
B) Does not wet the solid.
C) Spreads completely over the solid surface.
D) Is repelled by the solid.
27. The work done in stretching a soap film of area A by a small amount dA is:
A) T * dA
B) 2 * T * dA
C) T / dA
D) dA / T
28. A needle can be made to float on the surface of water due to:
A) Its low density.
B) Buoyancy.
C) Surface tension of water.
D) Adhesion to water.
29. When a solid is immersed in a liquid, the shape of the liquid surface near the solid is determined by the balance between:
A) Cohesive and gravitational forces.
B) Adhesive and surface tension forces.
C) Cohesive and adhesive forces.
D) Surface tension and pressure difference.
30. The unit of surface tension in the CGS system is:
A) N/m
B) J/m^2
C) dyne/cm
D) Pa.s
31. If the radius of a spherical liquid drop is halved, its surface energy will:
A) Remain the same
B) Decrease by a factor of 2
C) Decrease by a factor of 4
D) Increase by a factor of 2
32. Which phenomenon is responsible for the spherical shape of small liquid drops?
A) Viscosity
B) Surface tension
C) Density
D) Capillarity
33. The excess pressure in a cylindrical liquid jet of radius R is:
A) T/R
B) 2T/R
C) T/(2R)
D) 4T/R
34. When two small air bubbles of radii r1 and r2 (r1 < r2) in water merge, the process results in:
A) Decrease in total surface energy.
B) Increase in total surface energy.
C) No change in total surface energy.
D) Change in surface tension of water.
35. If a liquid drop of radius R has surface tension T, its surface energy is proportional to:
A) R
B) R^2
C) R^3
D) 1/R
36. What is the reason for excess pressure across a curved surface of a liquid?
A) Gravitational pull on the liquid.
B) Surface tension trying to minimize the surface area.
C) Viscous forces within the liquid.
D) Evaporation from the surface.
37. For a soap bubble in air, the excess pressure inside is given by:
A) 2T/R
B) 4T/R
C) T/R
D) 8T/R
38. The excess pressure inside a spherical liquid drop compared to the outside is given by:
A) 2T/R
B) 4T/R
C) T/R
D) 8T/R
39. When a liquid is depressed in a capillary tube, it indicates that:
A) Adhesive forces are greater than cohesive forces.
B) Cohesive forces are greater than adhesive forces.
C) The liquid wets the surface.
D) The surface tension is very low.
40. A liquid will rise in a capillary tube if the adhesive forces between the liquid and the tube walls are:
A) Stronger than the cohesive forces within the liquid.
B) Weaker than the cohesive forces within the liquid.
C) Equal to the cohesive forces within the liquid.
D) Zero.
41. For pure water in contact with clean glass, the angle of contact is approximately:
A) 0 degrees
B) 30 degrees
C) 90 degrees
D) 150 degrees
42. If the angle of contact is obtuse (greater than 90 degrees), the liquid is said to:
A) Wet the surface.
B) Be repelled by the surface.
C) Form a convex meniscus.
D) Have strong adhesive forces.
43. For a liquid that wets the solid surface, the angle of contact is typically:
A) Greater than 90 degrees
B) Equal to 90 degrees
C) Less than 90 degrees
D) Equal to 180 degrees
44. The angle of contact between a liquid and a solid surface depends on:
A) The nature of the liquid only.
B) The nature of the solid only.
C) The nature of the liquid-solid interface.
D) The volume of the liquid.
45. An increase in temperature generally leads to a decrease in surface tension because:
A) Intermolecular forces become stronger.
B) Kinetic energy of molecules increases, weakening cohesive forces.
C) The density of the liquid increases.
D) The viscosity of the liquid increases.
46. Surface tension of a liquid is independent of:
A) Temperature
B) Nature of the liquid
C) Presence of impurities
D) Area of the surface
47. The relationship between surface energy (E) and surface tension (T) for a liquid is:
A) E = T * A
B) E = T / A
C) T = E * A
D) T = E / A
48. Which of the following units is NOT used for surface tension?
A) N/m
B) J/m^2
C) dyne/cm
D) Pa.m
49. Surface tension is defined as the force acting per unit:
A) Area
B) Volume
C) Length
D) Mass
50. What is surface energy of a liquid?
A) The energy required to increase the surface area of the liquid by a unit amount.
B) The potential energy stored in the liquid due to intermolecular forces.
C) The kinetic energy of molecules at the surface of the liquid.
D) The work done to move a molecule from the bulk to the surface.
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