Surface Tension

Definition

Surface tension is a physical property of liquids that describes the cohesive forces at the surface of a liquid, causing it to behave as if its surface is covered with an elastic film. This phenomenon occurs due to the attraction between liquid molecules, which are more strongly attracted to each other in the bulk of the liquid than at the surface, leading to minimized surface area. Surface tension plays a critical role in various processes involving water, affecting its interactions with solids and gases, and influencing biological systems.

5 Must Know Facts For Your Next Test

1. Surface tension is typically measured in force per unit length, expressed in newtons per meter (N/m).
2. Water has one of the highest surface tensions of all liquids due to strong hydrogen bonding between water molecules.
3. Surface tension allows small objects, like a needle or water strider insect, to float on water without sinking despite being denser than water.
4. The temperature of a liquid affects its surface tension; generally, as temperature increases, surface tension decreases due to increased molecular motion.
5. Detergents and surfactants can reduce surface tension by disrupting cohesive forces among liquid molecules, allowing for improved cleaning and spreading properties.

Review Questions

• How does cohesion contribute to the phenomenon of surface tension?
  • Cohesion refers to the attraction between similar molecules, and in liquids like water, this force is particularly strong due to hydrogen bonding. At the surface of a liquid, molecules experience greater cohesive forces from those adjacent to them than from those above, which creates an inward pull. This effect results in the formation of a 'film' on the liquid's surface, leading to surface tension that allows objects with higher density than water to float.
• Discuss the effects of temperature on surface tension and why this relationship is significant for environmental processes.
  • Temperature has a direct impact on surface tension; as temperature rises, the kinetic energy of molecules increases, reducing the cohesive forces that contribute to surface tension. This relationship is significant for environmental processes such as evaporation and condensation. For instance, warmer temperatures can lead to lower surface tension in bodies of water, affecting how pollutants spread and how aquatic organisms interact with their environment.
• Evaluate how surface tension plays a crucial role in both biological systems and environmental chemistry.
  • Surface tension is vital in biological systems, influencing processes such as respiration in insects that rely on surface tension for movement across water surfaces. In environmental chemistry, it affects phenomena like water's ability to penetrate soil and carry nutrients, impacting plant growth and ecosystem health. Additionally, understanding surface tension helps in addressing pollution control strategies since it governs how contaminants disperse in aquatic environments. These roles underscore its importance across multiple fields of study.

Related terms

Cohesion: The attractive force between molecules of the same substance, which contributes to the formation of surface tension in liquids.

Adhesion: The attractive force between molecules of different substances, which can affect how a liquid spreads across a surface.

Capillary Action: The ability of a liquid to flow in narrow spaces without external forces, which is driven by the combined effects of cohesion and adhesion.