Soumyadip Moitra*, Shamsad Begam
The surface tension of water is an important parameter for many physical, chemical, biological and industrial processes. The surface tension of any liquid is positive, which can be understood from the fact that on average a molecule on the surface has fewer neighbours and hence fewer attractive van der Waals interactions than a molecule in the bulk. Here we are trying to show that the variation of surface tension of pure water with addition of chemical impurities such as soap, detergent powder and chilli powder by using a normal blade. Again, from the knowledge of this simple experiment we can also able to distinguish between normal water and soapy water (i.e. impure water). In practice, if there is a very small amount of soap or detergent mixed with water then that cannot be identified with naked eye and drinking that water may cause some adverse effects on our health. So, by putting a simple blade in our water sample we can easily tell identify whether the water sample is pure or not.
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