The value of surface tension of a liquid at critical temperature is

In most liquids, with a rise in temperature, the surface tension of the liquid

It is easier to spray water to which soap is added because the addition of soap to water:

If a drop of liquid breaks into smaller droplets,it results in the lowering of the temperature of the droplets. Let a drop of radius $R$ break into $N$ small droplets,each of radius $r$. Estimate the drop in temperature.

Describe a simple experiment for the measurement of the surface tension of a liquid.

When water is heated,bubbles form at the bottom and detach to rise. Let the radius of the bubble be $R$. The bubble is in circular contact with the bottom of the container with a radius $r$. If $r \ll R$ and the surface tension of water is $T$,find the value of $r$ just before the bubble detaches from the container. (Density of water is $\rho_w$)