Surface Tension

Definition

Surface tension is a property of liquids that arises from the cohesive forces between the molecules at the surface of the liquid, which allows the surface to behave like an elastic sheet. This property is crucial in understanding the behavior of fluids, their density, and the pressure exerted by them.

5 Must Know Facts For Your Next Test

1. Surface tension is responsible for the formation of droplets and the ability of some insects to walk on water.
2. The strength of surface tension is influenced by the type of liquid, with liquids like water having a higher surface tension than liquids like alcohol.
3. Surface tension is a key factor in the design of microfluidic devices, where the manipulation of small volumes of liquids is crucial.
4. The addition of surfactants, such as detergents, can reduce the surface tension of a liquid, allowing it to spread more easily.
5. Surface tension plays a vital role in the functioning of the alveoli in the lungs, where it helps to reduce the work required for breathing.

Review Questions

• Explain how surface tension affects the behavior of fluids and the pressure exerted by them.
  • Surface tension is a crucial property that influences the behavior of fluids, including their density and the pressure they exert. The cohesive forces between the molecules at the surface of a liquid create an elastic-like sheet, which affects how the fluid interacts with its surroundings. For example, surface tension is responsible for the formation of droplets and the ability of some insects to walk on water. It also plays a role in capillary action, where liquids can flow through narrow spaces without the assistance of external forces like gravity. Additionally, surface tension contributes to the formation of the curved upper surface of a column of liquid, known as the meniscus, which is an important consideration in the study of fluid pressure.
• Describe the relationship between surface tension and the design of microfluidic devices.
  • Surface tension is a critical factor in the design and operation of microfluidic devices, which involve the manipulation of small volumes of liquids. In these systems, the ratio of surface area to volume is much higher than in larger-scale systems, making surface tension effects more prominent. The ability to control and manipulate surface tension, such as through the use of surfactants, is crucial for ensuring the desired flow and behavior of liquids within microfluidic devices. Engineers and researchers must carefully consider the surface tension properties of the liquids and materials used in the design of these miniaturized systems to optimize their performance and functionality.
• Analyze the role of surface tension in the functioning of the alveoli in the human lungs and explain how it helps to reduce the work required for breathing.
  • Surface tension plays a vital role in the functioning of the alveoli, the tiny air sacs in the human lungs where gas exchange occurs. The alveolar walls are covered with a thin layer of surfactant, a substance that reduces the surface tension of the liquid lining the alveoli. This reduced surface tension helps to minimize the work required for the lungs to expand during inhalation and contract during exhalation. Without this surface tension-lowering effect of surfactant, the alveoli would be more likely to collapse, making it much more difficult to breathe. The relationship between surface tension and the functioning of the alveoli is a prime example of how this fundamental property of liquids has important physiological implications for the human body.

Related terms

Cohesive Forces: The attractive forces between like molecules that hold a substance together, contributing to the surface tension of a liquid.

Capillary Action: The ability of a liquid to flow through narrow spaces or tubes without the assistance of, and in opposition to, external forces like gravity, due to the effects of surface tension.

Meniscus: The curved upper surface of a column of liquid, which is the result of surface tension and the adhesive forces between the liquid and the container walls.