Power point presentation about surface tension for class IX

1. WELCOME

2. SURFACE TENSION
DONE BY,
AISWARYA.S
PHYSICAL SCIENCE
REG.NO.13973001
KUCTE,KOLLAM

3. Surface tension is a contractive tendency of the
surface of a liquid that allows it to resist an
external force. Surface tension is an important
property that markedly influences the ecosystem.

4. •Surface tension is
exposed, for example, any
time an object or insect
(e.g. water striders) that is
denser than water is able
to float or run along the
water surface.

6. Forces acting on liquid

7. •The cohesive forces among liquid molecules are responsible for the phenomenon of
surface tension.
•In the bulk of the liquid, each molecule is pulled equally in every direction by neighboring
liquid molecules, resulting in a net force of zero.
•The molecules at the surface do not have other molecules on all sides of them and
therefore are pulled inwards.
•This creates some internal pressure and forces liquid surfaces to contract to the minimal
area. Surface tension is responsible for the shape of liquid droplets.
•Although easily deformed, droplets of water tend to be pulled into a spherical shape by
the cohesive forces of the surface layer.
• In the absence of other forces, including gravity, drops of virtually all liquids would be
approximately spherical. The spherical shape minimizes the necessary "wall tension" of the
surface layer according to Laplace's law.

8. Effects of surface tension

9. Water striders stay atop liquid surface due to surface
tension

10. Paper clip floats on water due to surface tension

11. Water beading on a leaf

12. Water dripping from a tap

13. Tears of wine

14. Water drops attain spherical shape due to surface
tension

15. Thank you