IGCSE Chemistry syllabus

• Solids have particles which are in very fixed arrangements and they vibrate around in fixed positions, they have little kinetic energy and there are strong forces between them
• Liquids have particles that are slightly more widely spaced apart, they're not touching quite as much so they have intermediate forces between them and they vibrate more and they don't have fixed positions
• Gases have particles that are further apart, they have large amounts of kinetic energy, they're not held in fixed position and there are weak forces between the particles
• Melting


  When a solid turns into a liquid
• Freezing


  When a liquid turns into a solid
• Boiling/Evaporating


  When a liquid turns into a gas
• Condensation


  When a gas turns into a liquid
• Particles with the most kinetic energy will evaporate first and leave the surface of the liquid, leaving the remaining particles with lower average kinetic energy
• In a closed container, condensation and evaporation will be occurring simultaneously
• Diffusion


  The net movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient, requiring no energy as it is a passive process
• In the ammonia and hydrochloric acid diffusion example, the white ring forms closer to the hydrochloric acid end because the 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 and cannot be split by chemical means
• Compound


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


  Contains two or more elements not chemically combined, that can be separated into its constituent components
• Molecule


  Two or more atoms bonded together
• Atom


  • Has a nucleus containing protons and neutrons, surrounded by shells of electrons
• Proton


  Has a mass of 1 and a positive charge of 1
• Neutron


  Has a mass of 1 and no charge (neutral)
• Electron


  Has a very small mass (1/2000 of a proton) and a negative charge of 1
• Atoms are uncharged because they have equal numbers of protons and electrons
• Atomic number


  The number of protons in an atom
• Mass number


  The total number of protons and neutrons in an atom
• Group number


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


  The number of electron shells in an atom
• Elements in the same group have similar chemical properties because they have the same number of electrons in the outer shell
• Noble gases


  Group 0 elements that are highly 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 the gain or loss of electrons
• In ionic bonding, metals form positive ions and non-metals form negative ions
• Covalent bonding


  Bonding between two non-metal atoms where they share electrons
• Covalent bonding diagrams


  • 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
• Ethene (C2H4) has a central carbon-carbon double bond with four hydrogen atoms
• Chemical structures


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


  Electrostatic forces of attraction between oppositely charged ions