Importance of Water in Life

Introduction

• Water covers over 70% of the Earth and composes around 70% of the human body.
• Essential due to its molecular structure and hydrogen bonding abilities.

Unique Characteristics of Water

1. Universal Solvent

   • Dissolves many substances due to its polarity and hydrogen bonding.
   • Sodium chloride (salt) dissociates in water due to attraction between water molecules and ions.
   • Importance:
     • Cells are mostly water, enabling frequent chemical reactions.
     • Organisms can respond to their environment.

2. Cohesion and Adhesion

   • Cohesion: Water molecules stick together due to hydrogen bonds.
   • Adhesion: Water molecules cling to other polar surfaces.
   • Importance:
     • Facilitates nutrient and waste transport in organisms.

3. High Surface Tension

   • Molecules at the surface are more attracted to each other than the air.
   • Effects:
     • Formation of water beads on surfaces.
     • Enables water striders to walk on water.

4. High Heat Capacity

   • Absorbs large amounts of heat without state change (liquid to gas).
   • Importance:
     • Stabilizes temperatures in lakes and oceans.
     • Helps organisms maintain stable internal temperatures.
     • Protects against rapid temperature changes.

5. Density Changes with Temperature

   • Water expands when it freezes due to hydrogen bond configuration.
   • Ice is less dense than water, so it floats.
   • Importance:
     • Bodies of water freeze from the top, acting as an insulator.
     • Protects aquatic life during winter by preventing complete freezing.

Conclusion

• Water's unique properties are critical for maintaining life and environmental stability.