Explain the difference between wetting agents and water-proof agents with respect to the phenomenon of surface tension.

Asked by MAANASI.M | 18th Nov, 2013, 07:11: AM

Expert Answer:

A substance that reduces the surface tension of a liquid, causing the liquid to spread across surface of a solid.
If such substances are added to the liquid, it lowers the surface tension and liquid can easily spread on the surface.
Contact angle is the angle a drop water makes with solid surface.
If contact angle is low liquid drop can easilly spread. Ex: water can easily wet the surface of a cottan cloth. Detergent also one example of wetting agent.
Water proof agents increases the surface tention hence the contact angle. Thus liquid can not spread on the surface. Ex: water beads on a wax or oily surface. water can not wet the oily surface because of high contact angle.

Answered by Komal Parmar | 19th Nov, 2013, 03:21: PM

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