What are the effects of (1) temperature on the angle of contact (2) impurity on the surface tension ?

Explanation

(1) Effect of temperature : The surface tension of a liquid decreases with increasing temperature of the liquid. Hence, the angle of contact also decreases with increasing temperature of the liquid.
(2) Effect of impurity : (1) The surface tension of a liquid increases with dissolved impurities like common salt. For dissolved impurities, the surface tension increases linearly with the concentration of the dissolved materials. (ii) It decreases with insoluble surface impurities like oil or grease and with sparingly soluble substances like phenol or alcohol.