Final answer:
Cohesive forces cause water droplets to bead on waxy surfaces due to the water molecules' attraction to each other, while adhesive forces allow water to spread on clean glass as it adheres more to the glass than itself. These forces are fundamental for the transport of water in plants and play a pivotal role in sustaining life.
Step-by-step explanation:
Attractive forces between molecules are essential for various natural processes and can be categorized into cohesive forces and adhesive forces. Cohesive forces bind molecules of the same type together, like water droplets on a waxy surface where water beads up due to the cohesion between its molecules being stronger than the adhesion to the waxy surface. Conversely, adhesive forces are seen when a liquid spreads out over a surface, such as water on clean glass, where the attraction between water molecules and glass is stronger, causing the water to 'wet' the glass.
Two examples where cohesive forces dominate are: water droplets on a waxed car surface, and mercury in a glass container, where it forms a convex meniscus as mercury molecules are more attracted to each other than the container's interior. On the other hand, two examples where adhesive forces dominate are water spreading on a clean glass surface and paint adhering to a wall.
Importance of Cohesive and Adhesive Forces in Life
Cohesive and adhesive forces are crucial for sustaining life. They enable water transport from the roots to the leaves in plants, a process necessary for plant nourishment. This 'pull' on the water column depends on cohesive and adhesive forces working together, allowing life-sustaining processes, such as photosynthesis, to occur.