I read that, 

> 
> Angle of contact decrease with the addition of impurities whereas it increases if the temperature is increased
> 
> 
> 

For the explanation of why it increases with increase in temperature, I found out that the surface tension causes the increase in cohesive forces and hence a upward concave. So when temperature rises, surface tension decreases and angle of contact increases. 

Is this explanation correct, and could you explain it in some other way or elaborate about it? 

And I was not able to find why does it decrease with increase in impurities 

Source:

[![From the Book: Self Study Guide for online BITSAT 2017](https://i.stack.imgur.com/9usia.jpg)](https://i.stack.imgur.com/9usia.jpg)

*From the Book: Self Study Guide for online BITSAT 2017*