Lecture Notes: Understanding Water

Introduction

• Discussion on water and its significance.
• Misconception: Water is only found in obvious places like oceans, pools, rivers, etc.
• Reality: Water is everywhere, including within living organisms.

Water in Living Organisms

• Humans consist of billions of cells.
• Cells are composed mainly of water (~70% water in living beings).
• Key Components:
  • Organelles within cells contain water.
  • Cytoplasm is primarily water.
  • Water exists between cells and in bodily fluids (blood, urine, etc.).

Basic Chemistry of Water

• Chemical formula: H2O, consists of one oxygen and two hydrogen atoms.
• Bonds:
  • Covalent bonds bind oxygen and hydrogen (strong, hard to break).
  • Water molecule structure is V-shaped.

Origin of Water on Earth

• Early Earth was hot with molten lava.
• Cooling of Earth allowed water to be retained.
• Water is crucial for the existence of life.

Molecular Structure of Water

• Water is polar: oxygen is slight negative (Δ-), hydrogen is slight positive (Δ+).
• Intermolecular Forces:
  • Hydrogen bonds form between water molecules (ephemeral, weaker than covalent bonds).

Properties of Water

• Cohesion and Adhesion:
  • Cohesion: Water molecules stick to each other (surface tension).
  • Adhesion: Water molecules stick to other surfaces.
  • Uses in nature: e.g., capillary action in plants.
• Solvent Properties:
  • Water is a universal solvent, dissolves polar substances (hydrophilic) but not nonpolar (hydrophobic).
  • Example: Salt dissolves in water; oil does not.

Physical Properties of Water

• Buoyancy: Water exerts upward force, allowing objects to float.
• Viscosity: Resistance to flow, affects movement through water.
• Specific Heat: High energy required to change water temperature.
• Thermal Conductivity: Efficient heat distribution within water.

Application to Wildlife

• Organisms adapt to water's properties (e.g., buoyancy, viscosity).
• Adaptations in creatures like ducks and seals for survival in water.

Summary

• Water’s ubiquity and its complex properties make it essential for life.
• Understanding water aids in comprehending broader biological concepts.

Practice Questions

• Understanding water's properties through multiple-choice and diagram-based questions.