Question

The surface tension of water is 7.28 ✕ 10−2 J/m2 at 20°C. Predict whether the surface tension of heptane would be higher or lower than that of water at the same temperature. Explain your answer.

Answer 1

Answer:

Lower  

Explanation:

Surface tension occurs because molecules at the surface do not have molecules above them, so they cohere more strongly to their neighbours.

The stronger cohesive forces make it more difficult to move an object through the surface than when it is beneath the surface.

The attractive forces in water are strong because of hydrogen bonding.

A hexane molecule is nonpolar, so the only attractions are the weak London dispersion forces.

The cohesive forces at the surface are much lower than those in water, so the surface tension of hexane is lower than that of water at the sane temperature.