key term - Surface Tension

Definition

Surface tension is a physical property of liquids that describes the elastic-like force at the surface of a liquid, caused by the cohesive attraction between liquid molecules. This phenomenon allows the surface of a liquid to behave like a stretched elastic membrane, impacting how liquids interact with solids, other liquids, and gases. Surface tension is crucial for various processes in food science, such as emulsification and foaming.

5 Must Know Facts For Your Next Test

1. Surface tension is measured in force per unit length, typically in dynes per centimeter (dyn/cm) or newtons per meter (N/m).
2. The surface tension of water is relatively high at about 72.8 dyn/cm at room temperature, which enables small insects to walk on its surface.
3. Temperature affects surface tension; as temperature increases, surface tension typically decreases due to increased molecular motion.
4. Surfactants are compounds that can significantly reduce surface tension by disrupting cohesive forces among liquid molecules, which is important in food emulsions.
5. Surface tension plays a key role in processes such as bubble formation and the stability of foam in products like whipped cream and meringue.

Review Questions

• How does surface tension impact the behavior of liquids when they come into contact with different surfaces?
  • Surface tension affects how liquids spread or bead when they touch different surfaces. When a liquid encounters a surface with high adhesion compared to its cohesion, it will spread out more. Conversely, if the cohesion between the liquid molecules is stronger than the adhesion to the surface, the liquid will bead up. This behavior is essential in applications like coating and emulsifying in food science.
• Discuss the role of surfactants in modifying surface tension and how this relates to food science applications.
  • Surfactants are substances that lower surface tension by interfering with the cohesive forces among liquid molecules. In food science, surfactants are vital for creating stable emulsions like mayonnaise or salad dressings by allowing oil and water to mix more effectively. By reducing surface tension, surfactants help stabilize bubbles in foams, which are important in products such as whipped cream and meringue.
• Evaluate how temperature changes influence surface tension and what implications this may have for cooking techniques involving liquids.
  • Temperature changes can significantly alter surface tension; as temperature rises, surface tension typically decreases due to increased kinetic energy among molecules. This has important implications for cooking techniques such as boiling or frying, where understanding how heat affects liquid behavior can influence how ingredients interact. For example, lower surface tension at higher temperatures can enhance heat transfer and improve emulsion stability during cooking processes.

Related terms

Cohesion: Cohesion refers to the attractive forces between molecules of the same substance, which contribute to the surface tension in liquids.

Adhesion:

Adhesion is the attraction between different substances, such as liquid molecules and solid surfaces, influencing how liquids spread or bead on surfaces.

Capillary Action:

Capillary action is the ability of a liquid to flow in narrow spaces without external forces, driven by the balance of cohesive and adhesive forces, and affected by surface tension.