Understanding Cohesion
Cohesion is the attractive force that exists between molecules of the *same* substance. These forces hold the molecules together, resisting separation. It is primarily responsible for a liquid's internal resistance to flow (viscosity) and its tendency to maintain a definite volume.
Molecular Basis of Cohesion
Cohesive forces arise from various intermolecular forces, such as hydrogen bonds, dipole-dipole interactions, and London dispersion forces. In water, strong hydrogen bonds between water molecules lead to high cohesive forces, making it an excellent example to study this phenomenon.
Cohesion in Action: Water Droplets
A common example of cohesion is the formation of water droplets. Water molecules are strongly attracted to each other, causing them to pull inward and minimize their surface area, resulting in spherical or near-spherical drops. This same principle allows insects like water striders to walk on the surface of water.
Importance and Applications
Cohesion plays a vital role in natural phenomena and various scientific applications. For instance, it contributes to water's high surface tension, which is crucial for capillary action in plants, allowing water to travel from roots to leaves. In materials science, strong cohesive forces are desirable in materials needing high tensile strength for structural integrity.