Water

Water

1. Bonding

   • covalent intramolecular
   • Intermolecular
     • Hydrogen bonding between water molecules
   • To other polar molecules - dipole dipole
   • to ions - ion dipole dipole

2. PROPERTIES

   • Odourless, colourless,
     • 0℃ freezing - 100℃ boiling = higher than other group 16 hydrides due to polar bonds
       • 78% of earths surface

3. LATENT HEAT

   • FUSION
     • solid -> liquid
   • VAPORISATION
     • Liquid -> gas
   • Q = N x L <-- latent heat value , FUSION OF WATER - 6.0kJ mol-1, VAPORISATION - 44.0 kJ mol-1

4. WATER CYCLE

   • PHOTOSYNTHESIS - A reaction that occurs in plants between CO2 and H2O in the presence of sunlight.
     • COMBUSTION - A rapid reaction with oxygen accompanied by the release of large amounts of heat (burning)
       • RESPIRATION - Using glucose and oxygen to produce CO2 and H2O and energy in the form of ATP
         • PRECIPITATION - The residue of a substance from a solution
           • TRANSPIRATION - When water is drawn up through a plant
             • CONDENSATION - The forming of larger water molecules to form liquid on a surface, going from gas to liquid state.
               • EVAPORATION - Water that is drawn up from the ground or ocean from heat

5. UNIVERSAL SOLVENT - Homogenous

   • Solution - A homogeneous mixture of a solute dissolved in a solvent
     • Solute - A substance that dissolves in a solvent
       • Solvent - A substance that is able to dissolve a solute
         • Colloid - A mixture where very small particles are spread throughout a liquid, solid or gas. They're bigger than single molecules but so small that they don't settle standing
           • Suspension - A heterogeneous mixture containing solid particles that are large enough to sink to the bottom if its left to stand.

6. If dissolving - attraction to water = internal attraction

7. SOLUBILITY TABLE

8. SNAPE

   • S = sodium Na+
     • N = Nitrate NO3-
       • A = Ammonium NH4+
         • Potassium K+
           • Ethanoate CH3COO-

9. When soild forms double displacement or precipitation reactions, Need solubility rules

10. Ionic compounds

    • balancing equations
      • ionic equations

11. DEFENITIONS

    • Solubility
      • saturated solution - on line
        • unsaturated solution - below the line
          • supersaturated - above the line

12. SOLUBILITY CURVES

    • SOLIDS usually positive gradient
      • LIQUIDS unclear pattern
        • GASES usually negative gradient

13. CRYSTALISATION

    • when temp falls less disolves
    • when water evaporates
    • SLOW COOLING - large crystals
    • FAST COOLING - small crystals

14. CONCENTRATION

    • describes amount of solute in a given volume of solution
      • HIGH SOLUTE = concentrated
        • LOW SOLUTE = dilute

15. CONCENTRATION

    • g/L
      • ppm
        • ppb
          • mg/L
            • ml/L
              • %

16. n = CV

    • n = no. of moles
    • c = mol L-1
    • V = litres

17. Dilution

    • When more solvent added without changing solute
      • C1V1 = C2V2
        • C = concentration
        • V = volume