AP BIOLOGY

Detailed explanation-1: -Soap works by disrupting the cohesive forces between molecules. When plain water is dropped on a penny, water molecules strongly attract one another and the resulting surface tension is high. This is observed by the bubble-like shape formed by the water as more drops are added to the penny’s surface.

Detailed explanation-2: -The attraction of water molecules to other substances, like soil or glass, is called adhesion. As drops of water are added onto a penny, the adhesive force between the water and the penny keeps the water from falling off. Cohesive forces are strong, but not unbreakable.

Detailed explanation-3: -When the surface tension of a liquid is much higher than the energy of the surface it is on, the water tends to bead up. If the surface tension of the water is lower than the material it is on, the water tends to spread out across the surface. This is called “wetting” the surface.

Detailed explanation-4: -Surface tension= the tightness across the surface of water that is caused by the polar molecules pulling on one another. The pulling forces the surface of the water into a curved shape. It also causes raindrops to form round beads when landing on a windshield of a car.

Detailed explanation-5: -Water has an unusually high surface tension because of the relatively high attraction of water molecules to each other through a web of hydrogen bonds, water has a higher surface tension than most other liquids.