Given, n identical drops (each of radius r) of liquid of surface tension T and density ρ coalesce to form single drop. The energy released in the processes is converted into heat. Find the increase in the temperature of drop.

When n drops coalesce to form a single drop, the energy released during the process is
 

When n drops coalesce to form a single drop, the energy released duri
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Explain that spraying results coldness.


The surface area of liquid increases, when the sprayed in small droplets. Work has to be done against the cohesive force to increase the surface area. This work is done at the cost of internal energy and hence the temperature of drop falls. 

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It is possible to produce a fairly vertical film of soap solution but not of pure water. Explain. 

When we form the vertical film of soap solution, soap particles being heavy shift to lower side of film and hence surface tension on upper


When we form the vertical film of soap solution, soap particles being

part is greater than the lower part which provides the necessary force to balance the weight of film, hence film is stable. But in vertical film of pure water surface tension forces are same at all the points i.e. on A' B' and C'D'. Therefore, a film of pure water will break in the absence of extra force required to balance the weight.

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How does the surface tension of water change with impurities?

Adding impurities that are slightly soluble, decreases the surface tension of water. For e.g., addition of soap, camphor etc. decreases the surface tension of water.

The surface tension of the water increases if the impurities are highly soluble. e.g. addition of sugar, common salt etc., increases the surface tension of water. 
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n identical drops (each of radius r) of liquid of surface tension T and density ρ coalesce to form single drop. The energy released in the process is converted into kinetic energy. Find the speed of drop.

Let R be the radius of big drop. Since on coalesce of droplets, the volume of liquid remains constant, therefore


Let R be the radius of big drop. Since on coalesce of droplets, the v

Let R be the radius of big drop. Since on coalesce of droplets, the v

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