How does the surface tension of a liquid change with temperature?

Give two practical illustrations of surface tension.

$A$ ring is cut from a platinum tube with an internal diameter of $8.5\, cm$ and an external diameter of $8.7\, cm$. It is supported horizontally from the pan of a balance so that it comes in contact with the water in a glass vessel. If an extra $3.97\, g$ weight is required to pull it away from the water,the surface tension of water is ......... $dyne\, cm^{-1}$.

Consider a circular ring of radius $1.4 \,cm$ lying on the surface of a liquid. If a vertical force of $0.022 \,N$ greater than the weight of the ring is required to lift this ring from the liquid surface,then the surface tension of the liquid is (in $\,Nm^{-1}$)

The property utilized in the manufacture of lead shots is

Detergents are added to water for removing dirt from clothes. Explain.