$A$ mercury drop of radius $10^{-3} \ m$ is broken into $125$ equal size droplets. Surface tension of mercury is $0.45 \ Nm^{-1}$. The gain in surface energy is $...... \times 10^{-5} \ J$.

The surface energy of a liquid drop is $U$. It splits up into $512$ equal droplets. The surface energy becomes (in $U$)

$A$ soap bubble of radius $\frac{1}{\sqrt{\pi}} \text{ cm}$ is expanded to radius $\frac{3}{\sqrt{\pi}} \text{ cm}$. The surface tension of the soap solution is $25 \text{ dyne/cm}$. The work done during expansion in $\text{erg}$ is:

The radius of a soap bubble is increased from $\frac{1}{\sqrt{\pi}} \text{ cm}$ to $\frac{2}{\sqrt{\pi}} \text{ cm}$. If the surface tension of water is $30 \text{ dynes/cm}$,then the work done will be ....... $ergs$.

The surface tension of a soap solution is $2 \times 10^{-2} \ N/m$. The work done in producing a soap bubble of radius $2 \ cm$ is:

Fill in the blanks:
$(i)$ If the molecules of a body repel each other,then the surface area ...... and the surface energy ...... (choose between 'increases' or 'decreases').
$(ii)$ If the molecules of a body attract each other,then the surface area ...... and the surface energy ...... (choose between 'increases' or 'decreases').