Physics 2009 JAMB Past Questions - Question 24: It is observed that water will wet a clean glass because the

Correct Answer

D

Explanation

Water wets a clean glass because of the phenomenon of surface tension and adhesive forces. Surface tension is a property of liquids that causes them to minimize their surface area. Water molecules are attracted to each other due to cohesive forces, and at the surface of the liquid, there are fewer neighboring water molecules to bond with. This creates an imbalance in the forces, causing the molecules at the surface to be attracted inward, effectively reducing the surface area and forming a kind of "skin" on the water's surface.

When water comes into contact with a clean glass surface, the adhesive forces between the water molecules and the glass molecules are stronger than the cohesive forces within the water itself. This results in the water molecules sticking to and spreading out on the glass surface. This is why water "wets" the glass, forming a thin, continuous film.

In summary, the wetting of a clean glass by water is due to the combined effects of surface tension, cohesive forces among water molecules, and adhesive forces between water and the glass surface. These forces cause water to spread and adhere to the glass, creating a thin, uniform layer of liquid.