Water and Life

  • Water is the only common substance to exist in the natural environment in all three physical states of matter

    • structure of water allows it to interact with other molecules

  • in water molecules, electrons of polar covalent bonds spend more time near oxygen than hydrogen

    • this makes the O atom negative and H positive

      • alows adjacent water molecules to form hydrogen bonds

Four of waters properties

  • cohesive behaviour

  • ability to moderate temp

  • expansion upon freezing

  • versatile solvent

Water molecules sticking to other water molecules (due to hydrogen bonding) - Cohesion

Water molecuiles to non waiter molecules - adhesion

Surface Tension - measure of how hard it is to rbeak the surface of a liquid

  • water has unusually high surface tension bc hydrogen bonding between molecules at air/water interface

Moderation of temp by water

  • Water absorbs heat from warmer air/rleases stored heat to cooler air

  • water can absorb or relase a large amount fo heat with only slight change in its own temp

    • water has a high specific heat

    • Specific heat of water is one calorie (amount of energy requires to raise 1 gram of water by 1 (kilocalorie)

  • High specific head is due to large number of hydrogen bonds within a sample of water (helps minimize temp fluctuations)

Evaporation Coolingt

  • Transformation of a substance from liquid to gas

  • Heat of vaporization - heat a liquid mus absord for 1g to become gas

  • As liquid evaporates, remaining surface cools, called evaporative cooling

  • helps stabilize temps in organisms and bodies of water

Solvent

  • solution - liquid that is a completely homogenous mixture of substance

  • solvent - dissolving agent of solution

  • solute - substance that is dissolved

  • aqueous solution - water is the solvent

Water is a versatile solvent due to polarity

  • When an ionic compound is dissolved in water, each ion is sorrounded by a sphere of water molecules called a hydration shell

Hydrophilic/Hydrophobic

  • phillic - affinity for water

  • phobic - opposite