Q6 of 24 Page 73

For a surface molecule

Molecules inside a liquid experience a similar force of attraction due to liquid molecules around it from all directions. Molecules on the surface experience force of attraction by the liquid molecules below it and the air molecules above it. The force of attraction of liquid-liquid is greater than that of liquid-gas. Hence, it experiences a net downward force. As a result of this, the potential energy of a surface molecule is more than that of a molecule inside.

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