Chemistry [PAPER 1] AQA

• A mixture consist of two or more elements or compounds that are not chemically combined together
• Separating mixtures :

  • Filtration
  • Crystallization
  • Simple distillation
  • Fractional distillation
  • Paper chromatography
• Relative atomic mass = sum of isotopic mass / sum of atomic mass
• Isotopes are atoms of the same element with different numbers of neutrons, giving a different overall mass number
• elements - substances made of only one type of atom
• Compounds - made of different types of atoms

  Compounds are chemically bonded together
• Development of the atomic model

  1. Dalton's model - solid sphere that could not be divided into multiple parts.
  2. Plum pudding model - a cloud of positive charge with electrons embedded in it.
  3. Alpha scattering experiment - lead to the discovery of electrons.
  4. Nuclear model - electrons orbit the nucleus but not at fixes positions.
  5. Bohr model - electrons orbit at fixed positions.
• Atoms and particles :

  • Neutrons have a relative charge of 0 and a relative mass of 1
  • Protons have a relative charge of +1 and a relative mass of 1
  • Electrons have a relative charge of -1 and a relative mass of 0