Surface tension, capillarity, drops and bubbles - One Line Questions

1. For mercury in a glass capillary tube, the angle of contact is approximately 140 degrees. Therefore, cos θ is approximately: — -0.64
2. For water in a glass capillary tube, the angle of contact is approximately 0 degrees. Therefore, cos θ is approximately: — 1
3. If the surface tension of water is 0.07 N/m, the excess pressure in a small air bubble of radius 0.1 mm inside water is: — 1400 Pa
4. The pressure inside a spherical liquid drop is greater than the atmospheric pressure by an amount equal to: — 2T/r
5. The excess pressure in a liquid film stretched between two surfaces is: — 2T/r
6. What is the excess pressure inside a spherical soap bubble compared to the atmospheric pressure? — 4T/r
7. The work done in forming a spherical drop of radius R from the material of the liquid is: — 4πR²T
8. What is the work done to expand a spherical soap bubble of radius R to radius 2R? — 6πR²T
9. Why is the excess pressure inside a soap bubble (4T/r) twice that of a liquid drop (2T/r) of the same radius? — A soap bubble has two free surfaces, while a drop has only one.
10. The surface tension of a liquid is the energy stored in the surface per unit: — Area
11. If a liquid surface is extended by pulling it apart, work is done against: — Cohesive forces
12. A liquid will not wet a solid surface if: — Cohesive forces are greater than adhesive forces.
13. In a capillary tube, if the liquid wets the walls (e.g., water in glass), the meniscus is: — Concave
14. In a capillary tube, if the liquid does not wet the walls (e.g., mercury in glass), the meniscus is: — Convex
15. Consider a large soap bubble and a small soap bubble in contact. The surface of contact between them will be: — Concave towards the smaller bubble.
16. A clean glass plate is dipped in mercury and is then withdrawn. The surface of mercury on the plate will be: — Convex upwards
17. If the radius of a capillary tube is doubled, the capillary rise will be: — Halved
18. Which of the following is a consequence of surface tension? — All of the above.
19. The height 'h' of capillary rise of a liquid of surface tension 'T' in a tube of radius 'r' is given by the formula (where θ is the angle of contact and ρ is the density): — h = (2T cos θ) / (ρgr)
20. Which intermolecular force is primarily responsible for surface tension in liquids? — Van der Waals forces
21. If the temperature of a liquid decreases, its surface tension generally: — Increases
22. Surface tension can be reduced by: — Increasing temperature.
23. A liquid drop of radius R has a certain surface energy. If it breaks into 8 identical smaller drops, what is the change in surface energy? — It increases.
24. Which of the following statements about surface tension is FALSE? — It is independent of the area of the surface.
25. The phenomenon of capillarity is utilized in: — All of the above.
26. Which of the following factors does NOT affect the surface tension of a liquid? — Volume of the liquid
27. What is the SI unit of surface tension? — Newton per meter (N/m)
28. If two soap bubbles of radii r1 and r2 coalesce, the radius of the new bubble r is given by: — r = sqrt((r1³ + r2³)/(r1 + r2))
29. What is the shape of a small air bubble inside a liquid? — Spherical
30. A liquid film on a loop of any shape tends to assume a shape that minimizes: — Surface area
31. The force acting on a unit length of a line drawn on the surface of a liquid is equal to: — Surface tension
32. When a needle is carefully placed on the surface of still water, it floats. This is an example of: — Surface tension
33. A man can float on water due to: — Both B and C
34. The force tending to minimize the surface area of a liquid is called: — Surface tension
35. The rise of liquid in a capillary tube is independent of: — Density of the liquid
36. Capillarity is the phenomenon of rise or fall of a liquid in a narrow tube. This is due to: — Surface tension and adhesive forces.
37. What is the effect of adding a surfactant (like soap) to water on its surface tension? — Surface tension decreases significantly.
38. How does temperature affect surface tension? — Surface tension decreases with increasing temperature.
39. The excess pressure inside a bubble is zero if: — Both A and B are true.
40. What causes a liquid drop to be spherical in shape? — Surface tension, which minimizes surface area.
41. Work done in increasing the surface area of a liquid film by 'dA' is given by: — 2T * dA
42. A capillary tube is inserted into a liquid. The liquid level in the tube is lower than the outside level. This indicates: — The liquid does not wet the tube.
43. The angle of contact between a liquid and a solid surface depends on: — All of the above.
44. The rise of water in a capillary tube is inversely proportional to: — The radius of the tube.
45. If two soap bubbles of radii r1 and r2 (r1 > r2) are joined by a tube, then air will flow from: — The smaller bubble to the larger bubble.
46. What is surface tension? — The tendency of liquid surfaces to shrink into the minimum surface area possible.
47. If a capillary tube is dipped in water and then lifted, the water column will break if the height of the tube is greater than the capillary rise. — True
48. The pressure at the bottom of a liquid drop is: — Minimum at the center.
49. If the angle of contact is acute, the liquid: — Wets the solid surface.
50. If the angle of contact is obtuse, the liquid: — Does not wet the solid surface.
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