chem full

• Solids


  • Particles in very fixed arrangements, vibrate around fixed positions, have little kinetic energy, strong forces between them
• Liquids


  • Particles slightly more widely spaced apart, not touching as much, have intermediate forces between them, vibrate more, don't have fixed positions
• Gases


  • Particles further apart, have large amounts of kinetic energy, not held in fixed positions, weak forces between them
• Conversions between states of matter


  1. Solid to liquid = Melting

  2. Liquid to solid = Freezing

  3. Liquid to gas = Boiling/Evaporating

  4. Gas to liquid = Condensation
• Evaporation occurs as particles with the most kinetic energy leave the surface of the liquid, leaving the remaining particles with lower average kinetic energy
• In a closed container, condensation and evaporation occur simultaneously
• Diffusion


  The net movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient, no energy required
• Diffusion example

  • Ammonia and hydrochloric acid in a glass tube, forming ammonium chloride ring
• The ammonium chloride ring forms closer to the hydrochloric acid end because ammonia has diffused further and faster due to its lower relative atomic mass
• Atom

  The smallest particle of a substance that can exist
• Element

  Contains only one type of atom, cannot be split by chemical means
• Compound


  Two or more elements chemically combined, cannot be separated back into constituent elements
• Mixture


  Two or more elements not chemically combined, can be separated into constituent components
• Molecule


  Two or more atoms bonded together, can be the same or different elements
• Atom structure


  • Nucleus containing protons and neutrons, surrounded by shells of electrons
• Proton


  Positive charge, mass of 1
• Neutron


  Neutral charge, mass of 1
• Electron


  Negative charge, mass of 1/2000
• Atoms are uncharged, have equal numbers of protons and electrons
• Atomic number

  Number of protons in an atom
• Mass number

  Total number of protons and neutrons in an atom
• Group number


  Number of electrons in the outer shell of an atom
• Period number

  Number of electron shells in an atom
• Elements in the same group have similar chemical properties due to the same number of outer shell electrons
• Noble gases are so unreactive because they have full outer electron shells
• Isotopes


  Atoms of the same element with the same number of protons but different numbers of neutrons
• Ion


  A charged particle formed by gaining or losing electrons
• Formation of ionic bonds

  1. Metal loses electrons to become positive ion

  2. Non-metal gains electrons to become negative ion

  3. Oppositely charged ions are attracted to form ionic bond
• Covalent bond

  Bond formed between two non-metals by sharing electrons
• Covalent bonding examples

  • Water (H2O)
  • Methane (CH4)
• Water (H2O) has a central oxygen atom with two hydrogen atoms coming to the side
• Hydrogen

  Has one electron in its outer shell
• Oxygen

  Has six electrons in its outer shell, which becomes full with eight electrons
• Methane (CH4) has a central carbon atom with four hydrogen atoms
• Carbon dioxide (CO2) has double covalent bonds
• Chemical structures


  • Giant covalent
  • Giant ionic
  • Giant metallic
  • Simple molecular
• Ionic bond


  Electrostatic forces of attraction between oppositely charged ions
• Giant ionic structures


  • Have high melting and boiling points due to strong electrostatic forces
  • Don't conduct electricity when solid as ions aren't free to move
  • Conduct electricity when molten/liquid as ions are free to move
  • Are brittle as layers of ions slide and repel
• Diamond


  • Has a giant tetrahedral structure with many strong covalent bonds
  • Has a high melting point
• Graphite


  • Has a layered structure with weak intermolecular forces between layers
  • Has a slightly lower melting point than diamond
  • Is used as a lubricant as layers can slide off each other
  • Conducts electricity due to free electrons