NEET UG - Surface energy and surface tension, angle of contact, excess pressure across curved surfaces One Line Questions & Answers

1. For pure water in contact with clean glass, the angle of contact is approximately: — 0 degrees

2. The angle of contact for mercury in a glass tube is approximately: — 140 degrees

3. 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: — 0.0063 J

4. The work done to form a spherical soap bubble of radius R from a flat film is: — (4 * pi * R^2) * T

5. 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: — 2 * pi * r * T * cos(theta)

6. The excess pressure inside a spherical liquid drop compared to the outside is given by: — 2T/R

7. For a soap bubble in air, the excess pressure inside is given by: — 4T/R

8. The excess pressure inside a spherical bubble formed due to aeration in a liquid is given by: — 2T/R

9. When a liquid is depressed in a capillary tube, it indicates that: — Cohesive forces are greater than adhesive forces.

10. Surface tension is defined as the force acting per unit: — Length

11. When a solid is immersed in a liquid, the shape of the liquid surface near the solid is determined by the balance between: — Cohesive and adhesive forces.

12. A liquid exhibits positive excess pressure across its curved surface when the surface is: — Convex towards the gas phase.

13. A clean glass plate is dipped in mercury and taken out. The surface of mercury on the glass plate will be: — Convex

14. When two small air bubbles of radii r1 and r2 (r1 < r2) in water merge, the process results in: — Decrease in total surface energy.

15. The relationship between surface energy (E) and surface tension (T) for a liquid is: — E = T * A

16. When a liquid rises in a capillary tube, the pressure just below the surface inside the tube is: — Less than the atmospheric pressure.

17. If the angle of contact is 0 degrees, the liquid: — Spreads completely over the solid surface.

18. Surface tension is a property of: — Liquids only

19. What is the reason for excess pressure across a curved surface of a liquid? — Surface tension trying to minimize the surface area.

20. For a liquid that wets the solid surface, the angle of contact is typically: — Less than 90 degrees

21. If the radius of a capillary tube is halved, the rise of the liquid in the tube will be: — Doubled

22. If a small drop of liquid is broken into N identical smaller droplets, the total surface energy will: — Increase

23. If the radius of a soap bubble is doubled, the excess pressure inside it will: — Decrease by a factor of 2

24. An increase in temperature generally leads to a decrease in surface tension because: — Kinetic energy of molecules increases, weakening cohesive forces.

25. What is the effect of adding a detergent to water on its surface tension? — It decreases the surface tension.

26. Which of the following statements about surface tension is INCORRECT? — It is independent of temperature.

27. A needle can be made to float on the surface of water due to: — Surface tension of water.

28. When a liquid is in equilibrium in a container, the surface of the liquid adjusts itself to: — Minimize its surface area.

29. Which of the following units is NOT used for surface tension? — Pa.m

30. The unit of surface tension in the CGS system is: — dyne/cm

31. Which factor does NOT affect the angle of contact? — Temperature of the liquid

32. The excess pressure across a convex surface of a liquid is: — Positive (greater than outside pressure)

33. The excess pressure across a concave surface of a liquid is: — Negative (less than outside pressure)

34. If a liquid drop of radius R has surface tension T, its surface energy is proportional to: — R^2

35. Excess pressure inside a bubble of radius R is proportional to: — 1/R

36. If the radius of a spherical liquid drop is halved, its surface energy will: — Decrease by a factor of 4

37. The excess pressure in a soap bubble is twice that in a liquid drop of the same radius because: — A soap bubble has two free surfaces.

38. A liquid will rise in a capillary tube if the adhesive forces between the liquid and the tube walls are: — Stronger than the cohesive forces within the liquid.

39. The phenomenon of capillarity is a consequence of: — Surface tension and adhesive forces.

40. The work done in stretching a soap film of area A by a small amount dA is: — 2 * T * dA

41. Which of the following correctly describes the relationship between surface tension (T), surface energy (E), and area (A)? — T = E/A

42. The force exerted by surface tension on a line of length L is: — T*L

43. The excess pressure in a cylindrical liquid jet of radius R is: — T/R

44. Surface tension of a liquid is independent of: — Area of the surface

45. What is surface energy of a liquid? — The energy required to increase the surface area of the liquid by a unit amount.

46. The angle of contact between a liquid and a solid surface depends on: — The nature of the liquid-solid interface.

47. The angle of contact is measured between: — The tangent to the liquid surface at the point of contact and the solid surface.

48. Which phenomenon is responsible for the spherical shape of small liquid drops? — Surface tension

49. Which of the following liquids has the highest surface tension at room temperature? — Mercury

50. If the angle of contact is obtuse (greater than 90 degrees), the liquid is said to: — Be repelled by the surface.

Surface energy and surface tension, angle of contact, excess pressure across curved surfaces - One Line Questions