Dr E. Ramanathan PhD | Class 11 Physics | Surface Tension
This problem is based on coalescience of liquid drops in the Surface Tension topic of Class 11 Physics.
Concept Explanation — Energy Released on Coalescence of Liquid Drops
When two small liquid drops merge (coalesce) to form a single larger drop, the total surface area decreases because the surface-to-volume ratio reduces. Since surface energy is directly proportional to surface area, this reduction leads to a release of surface energy in the form of heat or kinetic energy.
4. Interpretation
- The merged drop has less total surface area.
- The difference in surface energy (due to reduced surface area) appears as released energy.
- Hence, energy released = decrease in surface area × surface tension.
Key Insight
Smaller drops have higher surface area per unit volume, meaning higher surface energy.
When they combine into a larger drop, the surface area reduces → surface energy decreases → energy is released.
