Surface Tension

Definition

Surface tension is the property of a liquid that allows it to resist an external force, due to the cohesive forces between liquid molecules at the surface. This phenomenon arises because molecules at the surface experience different forces than those in the bulk of the liquid, leading to a 'skin-like' effect. The importance of surface tension is evident in various biological processes, including how water interacts with cells and how organisms adapt to their environments.

5 Must Know Facts For Your Next Test

1. Surface tension is primarily caused by cohesive forces between water molecules, which are particularly strong due to hydrogen bonding.
2. The value of surface tension for water at room temperature is approximately 72 mN/m, making it one of the highest among common liquids.
3. Surface tension allows small insects, like water striders, to walk on the surface of water without sinking.
4. The presence of surfactants can significantly reduce surface tension, enabling processes like emulsification and cleaning.
5. In biological systems, surface tension plays a crucial role in processes such as alveolar function in lungs and nutrient absorption in plant roots.

Review Questions

• How does cohesion contribute to the phenomenon of surface tension, and what role does this play in biological systems?
  • Cohesion refers to the attraction between similar molecules, which is crucial for the formation of surface tension. In water, strong hydrogen bonds create a network of interactions that result in a high degree of cohesion at the surface. This allows organisms to utilize surface tension for various functions, such as insects walking on water or plants absorbing water through their roots. Without cohesion and the resulting surface tension, these vital processes would be severely hindered.
• Discuss how the properties of surface tension can impact ecological interactions within aquatic environments.
  • Surface tension affects how organisms interact within aquatic environments by influencing behaviors such as locomotion and feeding. For example, some small aquatic insects can exploit surface tension to move across water without breaking through. Additionally, surface tension plays a role in how droplets form on leaves or other surfaces, impacting water availability for plants and affecting nutrient cycling. Thus, surface tension not only facilitates individual organism behaviors but also contributes to broader ecological dynamics.
• Evaluate the significance of surfactants in modifying surface tension and how this knowledge can be applied in medical or environmental contexts.
  • Surfactants are agents that reduce surface tension by disrupting cohesive forces between liquid molecules. This property is essential in medical applications such as pulmonary surfactants that reduce surface tension in alveoli, preventing lung collapse during breathing. In environmental contexts, surfactants can be used to enhance oil spill clean-up efforts by allowing oil to disperse more easily in water. Understanding how surfactants modify surface tension is crucial for developing effective strategies in both healthcare and environmental management.

Related terms

Cohesion: The attractive force between similar molecules that helps hold them together, contributing to the formation of surface tension.

Adhesion: The attractive force between different substances, which can affect how liquids spread and interact with surfaces.

Hydrophilic: Describes substances that have an affinity for water and can interact favorably with water molecules.