A1.1 Water

• water is the medium for life
• water is a solvent required for metabolic reactions
• water is involved in hydrolysis reactions and photosynthesis
• water is a polar covalent molecule; with a negative oxygen atom and two positive hydrogen atoms. This is called hydrogen bonding.
• water is polar because the oxygen atom in the molecule has a greater attraction to the (negatively charged) electrons due to its' positively charged nucleus
• electrons are shared unequally in water molecules
• water molecules have 2 properties; cohesion and adhesion
• cohesion is the attraction between two water molecules (the same molecules)
• adhesion is the attraction of a water molecule to a different molecule (h2o to xylem water)
• both cohesion and adhesion form hydrogen bonds
• surface tension is a property water exhibits that showcases a substance ability to resist an external force
• water is cohesive, therefore it has a relatively strong/large surface tension
• xylem vessels are thin narrow tubes that transport water in plants (from roots to leaf)
• capillary action is a process relying on the adhesion of water to other molecules. It describes the ability of water to flow against gravity in a narrow space (xylem)
• metabolic reactions only occur when hydrophilic substances can dissolve in water
• water is a transport medium in plants and animals
• heat is transported around the body through water
• water does not dissolve hydrophobic substances such as lipids
• physical properties of water determine an animals aquatic habitats
• buoyancy, a physical property of water is the upward force exerted by a fluid on an object immersed in the fluid i.e. the ringed seal, this allows them to float in water with minimal energy
• viscosity, a physical property of water, is the measure of a fluids resistance to flow (High viscosity means harder to flow). the black-throated loon have a streamlined body shape that allows them to move in water.
• thermal conductivity, a physical property of water, is how well a material can conduct heat. Ringed seals have a layer of insulating rubber preventing heat loss and black-throated loons are insluated by their feathers.
• specific heat capacity, a physical property of water, is the energy required to raise the temperature of 1g of a substance to 1k. Endotherms are resistant to these changes.