The energy ($E$) required to form a liquid drop or bubble is equal to the work done against surface tension to increase its surface area.

1. Identify Surfaces: A soap bubble consists of a thin film of liquid, which has two surfaces (one inner and one outer) in contact with air. Therefore, the total surface area is $2 \times 4\pi r^2$.
2. Formula: $E = T \times \Delta A = T \times (2 \times 4\pi r^2)$.
3. Calculation: Radius, $r = 2 \text{ cm} = 0.02 \text{ m}$ Surface Tension, $T = 0.03 \text{ N m}^{-1}$ $E = 0.03 \times 8 \times 3.14159 \times (0.02)^2$ $E = 0.24 \times 3.14159 \times 0.0004$

• $E \approx 3.0159 \times 10^{-4} \text{ J}$

Rounding to two decimal places gives $3.01 \times 10^{-4} \text{ J}$.