AP BIOLOGY

Detailed explanation-1: -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-2: -What allows us to get such a large dome of water on top of the penny? Water has a high surface tension. This happens because water molecules like to stick together. This property is called cohesion.

Detailed explanation-3: -One reason that this happens is because of a property of water called cohesion. Cohesion is when two molecules that are similar to each other stick together. Water molecules are the same, and so they stick together and help keep drops on top of the penny.

Detailed explanation-4: -Gravity flattens the droplets, cohesion holds the droplets together, and adhesion holds the drops on the surface of the coin. The cohesive force is the pull of the water molecules on themselves. Each successive drop sticks to the water that’s already on the coin. We often call this cohesive force “surface tension”.