PAPER 1

• Substances are made of atoms, the different types of atoms are represented in the periodic table by a symbol
• Compound


  A substance that contains two or more different types of atoms chemically bonded together
• For every one oxygen atom there are two hydrogen atoms
• If there's no number after a symbol, there's an invisible one
• Chemical reactions


  Atoms change what they're bonded to and how they're bonded
• Word equation


  A way to represent a chemical reaction
• Chemical equation


  A way to represent a chemical reaction using symbols
• Atoms are not created or destroyed in any chemical reaction, there must be the same number of each type of atom on both sides
• Balancing chemical equations


  Start balancing atoms that are only in compounds, then balance the remaining elements
• Mixture


  Any combination of any different types of elements and compounds that aren't chemically bonded together
• Solution


  A mixture of a solute (dissolved substance) and a solvent
• Separating mixtures


  1. Filtration (for large insoluble particles)

  2. Crystallization (to leave a solute behind after evaporating the solvent)

  3. Distillation (to separate liquids with different boiling points)
• These are all physical processes, not chemical reactions, as no new substances are being made
• States of matter


  • Solid (particles vibrate around fixed positions)
  • Liquid (particles can move past each other)
  • Gas (particles move randomly and have the most energy)
• Gases can be compressed, while solids and liquids cannot
• To melt or evaporate a substance, you must supply energy, usually in the form of heat, to overcome the electrostatic forces of attraction between the particles</b>
• These physical changes do not involve breaking chemical bonds
• Atomic models


  • JJ Thompson's plum pudding model
  • Rutherford's discovery of the nucleus and mostly empty space
  • Bohr's discovery of electron shells/orbitals
  • Chadwick's discovery of neutrons
• Protons


  Positive charges in the nucleus
• Electrons


  Negative charges orbiting the nucleus
• Neutrons


  Neutral charges in the nucleus
• Atomic number


  The number of protons in the nucleus, determines the element
• Mass number


  The total number of protons and neutrons in the nucleus
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Relative abundance


  The percentage of each isotope in a sample
• The periodic table was originally ordered by atomic weight, then later grouped by properties
• Electron configuration


  The arrangement of electrons in shells around the nucleus
• Sections of the periodic table

  • Metals (left of staircase)
  • Non-metals (right of staircase)
  • Transition metals
• Group


  The column an atom is in, indicates the number of electrons in the outer shell
• Groups


  • Group 1 (alkali metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Ions


  Atoms that have gained or lost electrons, no longer neutral
• Metallic bonding


  Bonding in metals, a lattice of positive ions with delocalized electrons
• Ionic bonding


  Bonding between a metal and a non-metal, where the metal donates electrons to the non-metal
• Covalent bonding


  Bonding between non-metals, where they share electrons to fill their outer shells
• Ionic compounds have high melting and boiling points, and can conduct electricity when molten or in solution
• Molecular ions


  Ions made up of more than one atom, e.g. OH-
• Salts


  Any ionic compound, not just sodium chloride
• In covalent bonding, the number of bonds an atom makes is the same as the number of electrons it needs to fill its outer shell
• Giant covalent structures


  Structures like diamond and graphite, where covalent bonds extend in all directions
• Graphite can conduct electricity due to delocalized electrons between the layers