Lecture Notes: Properties of Water

Interconnectedness and Emergent Properties

• Interconnectedness among water molecules arises from extensive hydrogen bonding and intermolecular forces.
• Leads to emergent properties such as adhesion, cohesion, and surface tension.

Adhesion

• Definition: Interaction between a liquid and a solid surface due to adhesive forces.
• Example: Water in a test tube forms an inverted meniscus, unlike mercury which forms an upward meniscus.

Cohesion

• Definition: Forces that hold water molecules together.
• Example: Water droplets forming on agave or taro leaves due to cohesive forces and hydrogen bonding.
• Cohesion helps in forming water droplets on non-polar surfaces like plastic or taro leaves.

Surface Tension

• Definition: Energy required to increase the surface area of water; dependent on cohesive forces.
• Example: Water striders can walk on water due to surface tension.
• Mechanism: Hydrogen bonds create a "cover" allowing weight to be carried on the surface.
• Explains phenomena like skipping stones on water surfaces.

Importance to Nursing

• Functions of Water in the Body:
  • Cell hydration
  • Fluid regulation
  • pH and thermal regulation
• Temperature Regulation:
  • High heat capacity: vital for cell transport and metabolism.
  • Evaporation during perspiration helps cool the body.
  • Freezing leads to formation of ice, which is less dense.

Temperature Effects on Water

• Increasing Temperature:
  • Breaks hydrogen bonds, leading to evaporation.
  • Perspiration results in cooling.
• Decreasing Temperature:
  • Forms hydrogen bonds, water becomes ordered and freezes.
  • Ice formation causes less density, allowing it to float.

Transpiration

• Definition: Movement of water through plants from roots to leaves.
• Mechanism: Involves adhesion and cohesion.
  • Water adheres to xylem and climbs up, carrying nutrients.

pH Regulation

• Definition: Measure of hydrogen and hydroxyl ions in water.
• Importance: Indicates chemical changes in water.
• pH Balance: Must be maintained for chemical stability.

Hydrophilic and Hydrophobic Interfaces

• Hydrophobic (non-polar): Repels water, e.g., oil in water creates separate layers.
• Hydrophilic (charged): Attracts water, forms bonds with water molecules.

Conclusion

• Review and assess comprehension of the discussed concepts.
• Importance of studying and understanding the properties of water for various applications.