What does adhesion describe?

• A. Water moving through soil as a gas
• B. Water evaporating from the surface
• C. Water sticking to water
• D. Water sticking to soil particles

Answer: (D)

Adhesion is the attraction between unlike substances, such as water and solid surfaces. In soils, adhesion means water molecules stick to soil particles, forming thin wetting films that can move through small pore spaces and promote capillary rise. This helps keep moisture in the root zone between rainfall events. By contrast, cohesion is water sticking to itself, which governs droplets and surface tension. The other options describe water moving as a gas or evaporating, which are about phase change and not the attraction between water and soil surfaces.