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OCR GCSE Chemistry Notes | C1

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  • Solids: particles are close together and vibrate in neat rows and columns.
  • Liquids: particles are close together and they move slowly.
  • Gases: particles are far apart, moving at random speeds and directions.
  • Chemical changes require a chemical reaction; the products are different from the reactants.
  • Physical changes require energy.
  • The particle model does not take into account: forces between particles, the size of particles, and space between them.
  • Changes of state: melting, evaporating, condensing, freezing, sublimation (solid to gas).
  • Dalton said: each element has unique atoms, they can't be divided.
  • Thomson: plum pudding model; positve ball with negative electrons dotted around.
    • he disproved that atoms can't be split using cathode-ray tube showing small particles inside an atom.
  • Rutherford: positive nucleus and negative electrons around.
  • Bohr said: electrons occupy shells.
  • Geiger & Marsden: carried Rutherford's experiment (shot alpha particles at gold foil). Most particles went straight through, few deflected and reflected proving that most of the atom is empty space.
  • An atom is a positive nucleus surrounded by negatively charged electrons (2, 8, 8), with the nuclear radius much smaller than that of the atom and with most of the mass in the nucleus.
  • Atomic radii: 10-10m.
  • Relative Mass: Proton (1), Neutron (1), Electron (0)
  • Relative Charge: Proton (+1), Neutron (0), Electron (-1)
  • Top number on periodic table: mass number (protons and neutrons)
  • Bottom number: proton number (no. of protons or electrons)
  • The number of protons is the same as the number of electrons for an uncharged element.
  • Ion: charged particle (gained or lost electrons).