Lecture Notes: Properties and Importance of Water

Introduction

• Water is a favorite molecule due to its unique properties.
• Makes up 3/4 of Earth's surface.
• Essential for life and biological processes.

Structure and Polarity

• Water is polar and shaped like an outstretched V.
• Oxygen is highly electronegative, holding electrons closer than hydrogen.
  • Oxygen gains a slightly negative charge.
  • Hydrogen gains a slightly positive charge.
• Hydrogen bonding occurs between water molecules.

Cohesion and Adhesion

• Cohesion: Water molecules stick together due to hydrogen bonding.
  • Allows water movement in plants (e.g., xylem in trees).
  • Contributes to surface tension, enabling insects to walk on water.
• Adhesion: Water molecules stick to other surfaces.
  • Helps in fighting gravity in plants.

Solvent Properties

• Water is a powerful solvent for polar molecules and ionic compounds.
• Essential for biological processes (e.g., kidney function, body fluids).

Density and Ice Formation

• Water expands and is less dense when frozen, forming ice.
  • Ice floats, providing insulation for aquatic life.
• Hydrogen bonds form a lattice in ice, maintaining lower density than liquid water.

Temperature Regulation

• High specific heat: Water resists temperature change.
  • Stabilizes aquatic environments.
  • Absorbs heat in summer, releases it in winter.
• Evaporative cooling: High-energy molecules evaporate, reducing heat on surfaces.
  • Important for cooling in animals and plants.

Conclusion

• Water's unique properties are crucial for life and environmental stability.
• Encouragement to stay curious about the natural world.