Which best explains the surface tension of water?
-capillary action
-cohesion
-adhesion
-sublimation
The Correct Answer and Explanation is:
The best explanation for the surface tension of water is cohesion.
Explanation:
Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic membrane. Water has a high surface tension, meaning its surface is more resistant to external force than that of many other liquids. This property is a result of the cohesion between water molecules. Cohesion refers to the attraction between molecules of the same substance. In water, this is due to the hydrogen bonds that form between the hydrogen atoms of one water molecule and the oxygen atom of another.
Water molecules are polar, with the oxygen atom being slightly negative and the hydrogen atoms being slightly positive. This polarity allows hydrogen bonds to form, which are relatively strong intermolecular forces. At the surface of the water, the molecules experience stronger cohesion because they are not surrounded by other water molecules on all sides, as is the case for molecules in the interior of the liquid. As a result, the molecules at the surface are pulled inward, creating a “skin” on the surface that resists deformation.
Capillary action, while related to surface tension, is not the cause of it. Capillary action refers to the ability of a liquid to flow in narrow spaces without the assistance of external forces, like gravity. It occurs when adhesion (the attraction between water molecules and the surface of a tube) and cohesion (the attraction between water molecules) work together.
Adhesion is the attraction between water molecules and other substances, such as when water sticks to a glass surface, but it is not the primary cause of surface tension.
Sublimation refers to the process where a substance changes from a solid to a gas without going through the liquid phase, and is not related to the concept of surface tension.
Thus, cohesion explains the surface tension of water by describing the attractive forces between water molecules that pull the surface molecules inward, creating the observed surface tension.