chemistry paper 1 seperates aqa

• Element


  Substance made from only one type of atom
• There are about 100 elements, listed on the Periodic Table
• Represent elements on the Periodic Table

  With a symbol
• The symbol for sodium is Na, not NA
• Compound


  Two or more atoms chemically bonded together
• How compounds are formed


  When elements react together
• Signs of a chemical reaction

  • New product formed
  • Temperature change
  • Colour change
  • Gas produced
• Diatomic element


  Element that always exists as two atoms bonded together
• Diatomic elements


  • N2
  • H2
  • O2
  • All of group 7
• Naming a compound when two elements react

  The compound name ends in -ide
• Naming a compound with 3+ elements, one being oxygen

  The compound name ends in the suffix -ate
• Molecule


  Particle made from atoms joined together by covalent bonds
• H2 has 2 atoms and 1 element
• NH4NO3 has 9 atoms and 3 elements
• Mixture


  Substances made of two or more types of atoms NOT chemically bonded together
• In a mixture, the chemical properties of the substances do not change
• Pure substance


  A single element or compound
• Checking if a substance is pure

  1. Melt it

  2. If melting point is lower than pure, it is impure

  3. If melts over a range of temperatures, it is impure
• Melting


  A solid turning into a liquid
• Condensation


  A gas turning into a liquid
• Freezing


  A liquid turning into a solid
• Evaporation


  A liquid turning into a gas
• Bromine has a melting point of -7oC and boiling point of 59oC, so at 25oC it is a liquid
• Caesium has a melting point of 28.5oC and boiling point of 671oC, so at 25oC it is a solid
• Soluble


  Can dissolve
• Insoluble


  Cannot dissolve
• Solute


  A solid which can dissolve
• Solvent


  A liquid in which a solid will dissolve
• Solution


  A mixture of a dissolved solute and solvent
• Filtration


  Separates an insoluble solid and a liquid
• Crystallisation


  Separates a soluble solid and a solvent (collects solid)
• Separating salt from salt water

  Crystallisation
• Saturated


  No more of the solute (the thing that dissolves in the solvent) can dissolve
• Obtaining dry crystals after crystallisation

  1. Filter the crystals

  2. Place in a warming or drying oven
• Crystallisation


  1. Heat a solution gently until saturated

  2. Crystals will start to form

  3. As solution cools, more crystals form

  4. Filter the crystals

  5. Dry them in a warming oven
• Simple distillation


  Separates a solute from a solution, where the solute has a much lower boiling point than the solvent
• Simple distillation


  1. The solvent boils

  2. The vapours pass through a condenser and condense

  3. The pure solvent is collected
• Fractional distillation


  Separates two or more liquids that have similar boiling points
• Chromatography


  Separates substances with different solubilities e.g. different colours of ink or dye
• Mobile phase in chromatography


  The solvent (that travels up the paper)