The surface tension (capillary rise) experiment Viva Questions and Answers
(i) Define surface tension
Ans: It is defined as the force acting tangential to the liquid surface and perpendicular to unit length of an imaginary line drawn on the surface of the liquid
(ii) What is the unit and dimension of S.T?
Ans: Unit-Nm-1; Dimension MLT-1
(iii) How is surface tension related to surface energy?
Ans: They are the same.
(iv) What is the difference between adhesive and cohesive forces?
Ans: Attraction between molecules of the same kind-cohesive. Attraction between molecules of different kind-adhesive.
(v) What is angle of contact?
Ans: The angle between the tangent to the liquid surface at the point of contact and the solid inside the liquid.
(vi) What is meant by capillarity?
Ans: Rise of liquid in capillary tube is called capillarity
(vii) For mercury there is capillary depression. Why?
Ans: Angle of contact is oblige (140 °)
(viii) What are the factors on which capillary ascent depends?
Ans: Inversely proportion to the radius, inversely proportional to density and directly proportional to surface tension.
(ix) If the angle of contact were 90°. What is capillary accent?
Ans: Zero
(x) Is surface tension is a molecular phenomenon or atomic
Ans: Molecular phenomena.
(xi). What is a capillary?
Ans: A tube with fine bore.
(xii). What is the unit of surface tension?
Ans: N/m
(xiii). Give the value of surface tension of water?
Ans: It is 72.7 x 10-3 N/m at 20° C
(xiv). Define capillary rise.
Ans: Rising of a liquid in a capillary tube is called capillary rise.
(xv). Why doesn't mercury rise in the capillary tube?
Ans: For mercury and clean glass, the angle of contact is obuse. Hence mercury does net rise in the capillary tube.
(xvi). Why does water rise in the capillary tube?
Ans: For water and clean glass, the angle of contact is acute. Hence water rises in the capillary tube.
(xvii). How does surface tension vary with temperature?
Ans: Surface tension decreases with increase in temperature.
(xvii) Aim of surface tension experiment?
Ans: To find the surface tension of water by capillary rise.
(xix) Apparatus for the Surface tension experiment?
Ans: A narrow capillary tube of uniform bore of known radius, beaker containing water, travelling microscope and so on.