9700 · 2.4
Water
Welcome to your comprehensive revision on water, a molecule so deceptively simple yet profoundly complex in its importance to life. Understanding water's **unique properties** is absolutely fundamental to AS Level Biology. From temperature regulation to nutrient transport, virtually every biological process relies on H₂O. Let's dive into why water is truly the 'solvent of life'.
Need to know
What you need to know
- Water is a polar molecule due to unequal electron sharing, leading to δ+ hydrogen and δ- oxygen atoms.
- Hydrogen bonds form between water molecules, underpinning all of its unique properties.
- High Specific Heat Capacity: Water resists temperature changes, providing a stable internal environment for cells and aquatic habitats.
- High Latent Heat of Vaporisation: Evaporation of water (e.g., sweat) provides a powerful cooling effect.
- Excellent Solvent: Water's polarity allows it to dissolve and transport polar solutes like glucose, ions, and waste products.
- Cohesion & Adhesion: These forces are responsible for surface tension and the movement of water up plant xylem (transpiration stream).
- Density Anomaly: Ice is less dense than liquid water, so it floats, insulating aquatic environments in winter.
- Metabolite: Water is a reactant in hydrolysis reactions (breaking down molecules) and a product in condensation reactions (building molecules).
Explanation
Water
- Water is a polar molecule due to unequal electron sharing, leading to δ+ hydrogen and δ- oxygen atoms.
- Hydrogen bonds form between water molecules, underpinning all of its unique properties.
- High Specific Heat Capacity: Water resists temperature changes, providing a stable internal environment for cells and aquatic habitats.
- High Latent Heat of Vaporisation: Evaporation of water (e.g., sweat) provides a powerful cooling effect.