Chemistry IGCSE

• States of matter


  • Solid: Fixed shape and volume, particles arranged in a fixed pattern and vibrate around a point, held together by strong forces
  • Liquid: Fixed volume, take the shape of their container, particles held together by weaker forces
  • Gases: No fixed volume or shape - move freely, held together by little to no forces
• Sublimation


  Solid → gas
• Deposition


  Gas → solid
• Saturated


  Can dissolve no more solute
• Pressure


  Directly proportional to temperature, inversely proportional to volume
• 1 mol of gas occupied 24dm^3
• Diffusion

  Net movement of particles from area of high concentration to area of low concentration
• Conditions for fast diffusion

  • Lower relative molecular mass
  • High temperatures
• Impure substances

  Melting point is lower, boiling point is higher. Both are over a range of temperatures, not precise
• Filtration


  Insoluble solids from a liquid
• Crystallisation


  Soluble solids from its solution
• Evaporation


  Soluble solids from its solution
• Simple Distillation


  Water from something (solvent from a solution)
• Fractional Distillation


  Related and gas liquids from each other
• Paper Chromatography


  Biological substances from a solution
• Filtration


  Insoluble solid trapped on filter paper (residue), remaining liquid (filtrate)
• Crystallisation


  Soluble solids are less soluble at lower temperatures. Once you evaporate some of the solution it becomes more concentrated and saturated. Once cooled down crystals form, which you may then filter out (copper sulphate from copper sulphate in water)
• Evaporation


  Evaporate the solvent (the part where things are dissolved into) to leave the solute (the dissolved part)(salt water)
• Simple Distillation


  Heat in flask, the water vapour will rise into the condenser which has a lower temperature, the vapour will condense into the beaker as distilled water (salt from water)
• Fractional Distillation


  A mixture of liquids rises and vapour condenses on glass beads/rods in the fractionating column. The temperature is lower towards the top of the column where the liquids condense and return to the flask. It then boils again and rises further up the column, increasing the amount of the lower boiling point liquid in the fractionating column which drips into the beaker. Once the temperature has exceeded the lower boiling point and approaches that of the higher boiling point liquid you swap the beakers out and collect the second liquid.
• Paper Chromatography


  Add water to ink and as all dyes have different solubilities in water the dyes will separate into rings. You need to use a locating agent for amino acids. Rf = distance moved of amino acids / distance moved by solvent
• Ion


  Charged particle
• Cation


  Positive ion
• Anion


  Negative ion
• The higher the charge on the ion the higher the melting and boiling point as the electrostatic forces are stronger and more energy is needed to overcome the forces
• Atom


  Smallest part of an element that can exist
• Element


  1 type of atom only
• Molecule


  Two or more atoms held together by covalent bonds
• Mixture


  Two or more elements or compounds which are not chemically combined
• Compound


  Two or more elements are chemically combined
• Proton


  Charge of 1+
• Neutron


  Charge of 0
• Electron


  Charge of 1-
• Both protons and neutrons have mass 1, electron is negligible
• There is an equal amount of protons and neutrons in an atom
• Nucleon mass


  Protons + neutrons
• Isotopes


  Atoms of the same element with the same proton number but different nucleon numbers
• Periods


  How many shells an element has
• Groups


  How many outer-shell electrons an element have, which determines how it will react
• Chemical changes


  A new substance is formed, an energy change has occurred, hard to reverse