. SURFACE TENSION BY CAPILLARY RISE METHOD AIM To determine surface tension of a liquid by capillary rise method. APPARATUS REQUIRED A beaker of Water, capillary tube, vernier microscope, double hole rubber stopper, a knitting needle, a short rubber tubing and retort clamp. FORMULA The surface tension of the liquid T hrσg N m - where T → Surface tension of the liquid ( N m – ) h → height of the liquid in the capillary tube (m) r → radius of the capillary tube (m) σ → Density of water ( kg m – ) (σ = kg m – ) g → Acceleration due to gravity (g = .
m s – ) DIAGRAM h - SURFACE TENSION BY CAPILLARY RISE METHOD EXPERIMENTAL SETUP Needle PROCEDURE ¾ A clean and dry capillary tube is taken and fixed in a stand ¾ A beaker containing water is placed on an adjustable platform and the capillary tube is dipped inside the beaker so that a little amount of water is raised inside. UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical ¾ Fix a needle near the capillary tube so that the needle touches the water surface ¾ A Vernier microscope is focused at the lower meniscus of the water and the corresponding reading is taken after coinciding it with the horizontal line of the cross wire. ¾ Tip of the needle is focussed using vernier microscope after coinciding it with horizontal line of the cross wire ¾ The difference between the two readings of the vertical scale gives the height (h) of the liquid raised in the capillary tube. ¾ Now to find the radius of the tube, raise the capillary tube and remove the beaker.
Carefully rotate the capillary tube so that the immersed lower end face towards you. ¾ Focus the capillary tube using Vernier microscope to clearly see the inner walls of the tube. ¾ Let the vertical cross wire coincide with the left side