Capillarity: Surface Tension and Liquid Surface
Determination of Cleansing Action of Detergents
(Using Capillary rise)
Synopsis
This project report explains about the surface tension and capillarity of liquid through a simple experiment of finding the capillarity of various detergents. Oil stains and grease on dirty clothes cannot be removed, using water alone, because water does not wet them. If detergents added , surface tension is decreased, the area of contact is increased. Detergent molecules have the shape of a hairpin, one of which is attracted to water and the other end to the molecule of the grease, thus forming a water grease interface and so the surface tension is reduced. The dirt can be removed and carried away by the flow of the water.
[pic]
Two capillary tubes of different radii are cleaned well by immersing in caustic soda, dilute metric acid and distilled water. The liquid rises in the tubes due to the surface tension. The liquid meniscus is seen in one tube. The microscope reading is taken. The needle N is adjusted such that it just touches the liquid surface. The differences between the two readings give the height of the liquid raised in the tube.
The first chapter explains surface tension and capillarity by taking examples from day to day life and from a simple experiment .it gives the definition of surface tension. It also explains cohesive and adhesive force. Explanation of surface tension based on molecular theory is also given in this chapter. It gives the reason why the shape of small drops are spherical whereas larger drops are elliptical. This chapter also gives a brief description of angle between the tangent to the liquid surface at the point of contact and solid surface inside the liquid, which is called angle of contact. The chapter also informs about the pressure difference across a liquid surface and excess pressure inside a drop. All basics of surface tension are covered in
(Using Capillary rise)
Synopsis
This project report explains about the surface tension and capillarity of liquid through a simple experiment of finding the capillarity of various detergents. Oil stains and grease on dirty clothes cannot be removed, using water alone, because water does not wet them. If detergents added , surface tension is decreased, the area of contact is increased. Detergent molecules have the shape of a hairpin, one of which is attracted to water and the other end to the molecule of the grease, thus forming a water grease interface and so the surface tension is reduced. The dirt can be removed and carried away by the flow of the water.
[pic]
Two capillary tubes of different radii are cleaned well by immersing in caustic soda, dilute metric acid and distilled water. The liquid rises in the tubes due to the surface tension. The liquid meniscus is seen in one tube. The microscope reading is taken. The needle N is adjusted such that it just touches the liquid surface. The differences between the two readings give the height of the liquid raised in the tube.
The first chapter explains surface tension and capillarity by taking examples from day to day life and from a simple experiment .it gives the definition of surface tension. It also explains cohesive and adhesive force. Explanation of surface tension based on molecular theory is also given in this chapter. It gives the reason why the shape of small drops are spherical whereas larger drops are elliptical. This chapter also gives a brief description of angle between the tangent to the liquid surface at the point of contact and solid surface inside the liquid, which is called angle of contact. The chapter also informs about the pressure difference across a liquid surface and excess pressure inside a drop. All basics of surface tension are covered in