Surface tension

Definition

Surface tension is the property of a liquid that allows it to resist external force due to the cohesive nature of its molecules. This phenomenon occurs because molecules at the surface experience a net inward force, which creates a 'film' effect that can support light objects and shape the liquid into minimal surface area forms. Surface tension plays a crucial role in various biological processes, including the behavior of water in living organisms and its interactions with different materials.

5 Must Know Facts For Your Next Test

1. Surface tension is significantly stronger in water than in many other liquids due to hydrogen bonding between water molecules.
2. This property allows small insects, like water striders, to walk on water without sinking.
3. Temperature can affect surface tension; as temperature increases, surface tension generally decreases because molecules move more freely.
4. Detergents and soaps can lower the surface tension of water, allowing it to better penetrate and clean surfaces.
5. Surface tension is critical in biological systems, influencing processes such as the movement of water in plants and the formation of cell membranes.

Review Questions

• How does cohesion contribute to the phenomenon of surface tension in liquids?
  • Cohesion is the attraction between similar molecules, which plays a key role in creating surface tension. In liquids like water, molecules at the surface experience greater cohesive forces with each other than with the air above them. This imbalance creates a net inward force that results in surface tension, allowing the liquid to maintain its shape and resist external forces.
• Discuss how temperature changes can influence the surface tension of a liquid and provide an example.
  • Temperature changes have a direct impact on surface tension. As temperature increases, the kinetic energy of molecules also increases, causing them to move more rapidly. This increased movement reduces the strength of cohesive forces among the molecules at the surface, thereby decreasing surface tension. An example is boiling water; as it heats up, the surface tension diminishes, making it easier for bubbles to form.
• Evaluate the importance of surface tension in biological systems and its implications for life.
  • Surface tension is vital in biological systems as it influences various physiological processes. For instance, it allows small organisms to move across water surfaces and enables water transport in plants through capillary action. Additionally, surface tension affects how cells interact with their environment, influencing nutrient absorption and waste removal. Understanding these roles highlights how essential surface tension is for sustaining life and maintaining ecological balance.

Related terms

cohesion:

The attractive force between similar molecules, which causes them to stick together, contributing to surface tension.

adhesion:

The attractive force between different types of molecules, which allows liquids to spread on surfaces and interact with other materials.

capillarity: The ability of a liquid to flow in narrow spaces without the assistance of external forces, often driven by surface tension and adhesion.