How do cohesion and adhesion explain capillary action?

Question

Vivian Aronson · Accepted Answer

Cohesion is the connection made between identical molecules, while adhesion is the connection between different ones.

Water molecules are drawn to each other by cohesion forces resulting from their hydrogen bonding. Adhesion forces cause water molecules to adhere to surfaces that carry charges, such as glass or the lining of a xylem vessel. The water molecules climb a little as a result of the surface charge drawing them to the other upper part of the surface where there isn't any water adhering to it. These molecules are still bound to other molecules below them by the hydrogen bond (adhesion), so they tend to draw those other molecules up as well. This process continues until a water column rises inside the tube. This process is restricted by the tube's diameter because a larger diameter results in a smaller water column that can ascend. This is because a larger column means that more water molecules will be drawn upward, increasing the force of gravity acting in the opposite direction of the capillary action.

Eli Ayoub · Answer

undefined Together, cohesion and adhesion allow capillary action to overcome gravity. Cohesion between water molecules causes them to be drawn up into a narrow tube; adhesion between water molecules and the tube's surface allows the water to climb the tube's walls. Adhesion is the attraction between molecules of the same substance, whereas cohesion is the attraction between molecules of different substances.