4.1 - Water

Properties of Water

• Polarity of Water:

  • Water is an inorganic compound consisting of hydrogen (H) and oxygen (O) elements.
  • A water molecule is a polar molecule because the shared electrons between oxygen and hydrogen are attracted towards oxygen which is more electronegative.
  • This polarity produces hydrogen bonds between water molecules, allowing water to act as a universal solvent.

• Cohesive Force and Adhesive Force of Water:

  • Cohesive force: Water molecules stick to one another due to hydrogen bonding.
  • Adhesive force: Water molecules stick to other surfaces (e.g., the wall of xylem vessels).
  • Both forces produce capillary action which allows water to enter and move up along the xylem vessels against gravity.

• Specific Heat Capacity of Water:

  • Water has a high specific heat capacity of $4.2{\text{ kJ kg}}^{-1}{}^{\circ }{\text{C}}^{-1}$.
  • This means $4.2\text{ kJ}$ of heat energy is required to raise the temperature of $1\text{ kg}$ of water by $1{}^{\circ }\text{C}$.
  • This property helps to absorb a lot of heat energy with minimal changes in temperature, which is crucial in maintaining the body temperature of organisms.

• Importance of Water in a Cell

  • Provides a medium for biochemical reactions in the cell.
  • Acts as a universal solvent that dissolves and transports organic substances (e.g., glucose, amino acids) and inorganic substances (e.g., mineral salts, oxygen).
  • Acts as a lubricant (constituent of mucus and synovial fluid) and helps in lubrication of joints.
  • Provides support and turgidity to plant cells.
  • Helps in temperature regulation through evaporation of sweat.