UNIVERSAL COLLEGE OF ENGG AND

TECH

Student name

1. Devarshi Pandya

2. Karan Patel

3. Manank Patel

Enrollment number

130460106040

130460106056

130460106059

WHAT IS SURFACE TENSION ?

Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force.

WHAT IS SURFACE TENSION ?

Surface tension can be defined as tensile force acting on the free surface of a liquid per unit length.

for example, any type an object that is denser than water is able to float or run along the water surface

SURFACE TENSION

This phenomenon explains about the surface tension•Consider the 3 molecules of the liquid .•The molecule 1 is attracted in all directions

Thus the resultant forces acting on a molecule 1 is zero.•But 2 molecule which is situated near the free surface is acted upon upward & downward directions.

The molecule 3 situated on the free surface of liquid is subjected only net resultant downward force

Thus ,the free surface of liquid acts like a very thin layer under tension on the surface of liquid

SURFACE TENSION ON LIQUID DROP

Consider a small liquid drop of radius ‘r’.

P= pressure intensity in side drop.d=diameter of droplet. = surface tension of liquid.

The force acting on half drop

Tensile force acting around the circumference of cut portionTensile force= x d

Pressure force on area

Pressure force on area = /4 x =p x /4 xUnder equilibrium conditions, these 2 forces will be equal & opposite

2d 2d

Pressure force on area

p x /4 x = x p=4 /

2d d

d

EFFECT OF TEMPERATURE ON SURFACE TENSION.

The surface tension depends directly upon the intermolecular cohesion,& since this cohesion is known to decrease with temperature rise, tension decrease

The surface tension of water varies from about 0.074 N/mAt 20 C to 0.0589 N/m at 100 C .The surface tension of some liquids at 20 C at atmospheric pressure are given below

EFFECT OF TEMPERATURE ON SURFACE TENSION.

liquid N/mKerosene 0.0277Glycerine 0.0633Benzene 0.0289mercury 0.514

EFFECT OF TEMPERATURE ON SURFACE TENSION.

EXAMPLES OF SURFACE TENSION

Thin blade or clip float on the surface of water.

EXAMPLES OF SURFACE TENSION

Mercury on smooth surface converts in to small balls

EXAMPLES OF SURFACE TENSION

Rain water comes to the earth surface in the form of circular balls.

EXAMPLES OF SURFACE TENSION

Rain water falls on the leaf it formcircular balls.