A1.1 Water
1.1.1: Water as a medium of Life
Water is essential for life due to its unique physical and chemical properties. It serves as auniversal solvent, a temperature buffer, a medium for metabolic reactions, and a vehicle for nutrient.
1.1.2: Hydrogen Bonding
Water molecules consist of one oxygen and two hydrogen atoms, forming a bent molecular shape with an angle of approximately 104.5°. The oxygen atom, being
more electronegative, pulls shared electrons closer, creating partial charges (δ⁻ on
oxygen, δ⁺ on hydrogen).
This polarity allows hydrogen bonds to form between water molecules. Hydrogen bonds are intermolecular attractions between the slightly positive hydrogen of one molecule and the slightly negative oxygen of another. These hydrogen bonds are weaker than covalent bonds but significant in large numbers, giving rise to water’s cohesive and thermal properties.
1.1.3: Cohesion
Cohesion refers to the attraction between water molecules, primarily due to hydrogen bonding. This property enables surface tension, which allows insects to walk on water and supports the formation of droplets
1.1.4: Adhesion Of Water Molecules
Adhesion is the attraction between water molecules and other polar or charged surfaces. Adhesion explains why water droplets cling tosurfaces, such as leaves or skin, and how water spreads across hydrophilic materials like cellulose in plant cell walls.
Hydrophilic means water-loving. These substances mix well with water because they have charges or are polar. Examples: salt, sugar, amino acids.
Hydrophobic means water-fearing. These substances do not mix with water
because they have no charges and are non-polar. Examples: oil, fat, wax.
1.1.5: Solvent Properties of Water
Water’s polarity makes it an effective solvent, allowing it to dissolve and transport polar and ionic substances essential for biological processes like nutrient transport and cellular reactions.
1.1.6: Properties of Water VS Air
1.1.7 & 1.1.8 : Origin of Water On Earth (HL)
While the origin of water is still unknown it is said to be extra-planetrary, brought to earth through astroids. The strong gravitational force on earth and the moderate tempreature is what keeps the water on earth in its liquid form.
Furthermore, earth is said to be in the goldilock zone; meaning the tempreature is not too hot for water to evaporate and its not too cold for it to freeze.