Lecture Notes: Unique Properties of Water

Introduction

• Focus on the unique properties of water in biological contexts.

Structure and Polarity

• Water is a polar molecule.
• Shaped like an outstretched V.
• Contains one electronegative oxygen atom and two hydrogen atoms.
  • Oxygen holds electrons more closely, gaining a slight negative charge.
  • Hydrogens have a slight positive charge.
• Leads to the formation of hydrogen bonds between water molecules.

Hydrogen Bonding

• Water molecules bond together via hydrogen bonds.
• Hydrogen bonds are crucial for water's unique properties.

Adhesion and Cohesion

• Adhesion: Water sticks to other surfaces (e.g., xylem walls in plants).
• Cohesion: Water molecules stick to each other.
  • Enables water to travel up plants against gravity.
  • Creates surface tension allowing insects to walk on water.

Solvent Properties

• Water is a powerful solvent for polar molecules and ionic compounds.
• Essential for biochemical processes in organisms (e.g., kidney function).
• Major component of body fluids.

Density and Freezing

• Water expands and becomes less dense when frozen.
• Ice forms a protective insulating layer.
• Important for aquatic life to survive under ice.

Temperature Regulation

• Water has a high specific heat.
  • Stabilizes temperatures in aquatic environments.
  • Absorbs heat in summer, releases heat in winter.

Evaporative Cooling

• Water evaporation helps cool organisms.
  • Fast-moving, high-energy molecules evaporate first.
  • Plants use evaporative cooling to regulate temperature.

Conclusion

• Water's properties are essential for life.
• Encouragement to stay curious about water and its roles.