Few Definitions: Solution - homogenous mixture (the same throughout or results in 1 solution) of 2 or more substances Solvent - substance that is usually present in the larger quantity Solute - substance that is usually present in the smaller quantity (dissolved in solvent)

Example: sugar (solute) in water (solvent)

Solubility - amount of solute that will disolve in a given quantity of solvent (if too much sugar in water then it won’t all dissolve)

Eg. oil is insoluble in water but sugar is soluble

Factors that affect Solubility

  • solubility depends on the forces of attraction between solute and solvent particles
  1. Solubility and intermolecular forces:
  2. Types of forces: i) Dipole-Dipole Attraction - the attraction between oppositely charged ends of two polar molecules. (i.e. water dissolving sugar)
    • hydrogen bonding ii) Ion dipole attraction - between ions and polar molecules

Golden Rule: “Like dissolves Like”

  • polar substances dissolve in polar solvents (salt in water)
  • non-polar substance dissolve in non-polar solvents (i.e grease in paint thinner)
  • use Electronegativity difference and symmetry (3D orientation of the compound) to determine the solubility of a compound in water. Water will only dissolve ionic and polar covalent compounds
  • Ionic compounds that are strongly attracted to each other will not dissolve well in water because they are more attracted to the oppositely charged ion than to water molecules

More factors that affect solubility:

  • Molecule / Particle Size - as particle size decreases solubility increases
    • The more surface area there is the more contact the particle has with the solvent
  • If bits are smaller it should dissolve more easily
  • More surface area = faster dissolving
  • If equal amount of grain sugar and sugar cube were placed in water grain sugar would dissolve first because of more exposure to water

Temperature Solids - solubility increases with increasing temperature Liquids - no effect Gases - solubility decreases with increasing temperature

  • energy breaks solid particles apart
  • increases K.E. which decreases solubility in gases

Pressure Gases - as pressure increases solubility Solid & Liquid - no effect gases have too much energy to stay in solution, gas paricles must be “forced” into solution

Unsaturated Solution - A solution that can still have more solute dissolve in the solvent Saturated Solution - A solution that cannot have any more solute dissolved in the solvent Supersaturated Solution (Very special case does not happen normally) - A special case where a saturated solution has been cooled to the point where more than the theoretical maximum solute stays dissolved in the solvent

Solubility curves are used to indicate how much solute can be dissolved in 100g of solvent at a given temperature

Grade 11 Chemistry Homework p.368 # 7 - 12 p.370 # 1 - 16