chem 1

• Balancing chemical equations


  1. Start balancing atoms that are only in compounds

  2. Can't change small numbers as that would change the compound

  3. Put numbers in front of elements or compounds to multiply them up

  4. Finish balancing elements that are not in compounds
• Mixture


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


  A mixture of a solute dissolved in a solvent
• Separating mixtures


  1. Filtration for large insoluble particles

  2. Crystallization to leave solute behind after evaporating solvent

  3. Distillation to separate liquids with different boiling points
• Physical changes


  • No new substances are being made
  • Breaking intermolecular forces, not chemical bonds
• States of matter


  • Solid - particles vibrate in fixed positions
  • Liquid - particles can move past each other
  • Gas - particles move randomly and have high energy
• Gases can be compressed, solids and liquids cannot
• To melt or evaporate a substance, energy must be supplied to overcome intermolecular forces
• Atomic models


  • 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, electrons, neutrons


  • Protons and electrons have equal and opposite charges of +1 and -1
  • Neutrons have no charge
• Atomic number


  Number of protons in the nucleus
• Mass number


  Number of protons and neutrons in the nucleus
• Isotopes


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


  Percentage of each isotope in a sample
• Development of the periodic table

  • Ordered by atomic weight
  • Grouped by properties
  • Gaps predicted and later filled
• Electron configuration


  Electrons fill up shells/orbitals in a specific order
• Periodic table sections


  • Metals - donate electrons
  • Non-metals - accept electrons
  • Noble gases - very unreactive
• Group


  Column in the periodic table, indicates number of outer shell electrons
• Ions


  Atoms that have gained or lost electrons, forming positive or negative charges
• Metallic bonding


  • Lattice of positive ions with delocalized electrons
  • Allows good conduction of electricity and heat
• Ionic bonding


  • Transfer of electrons between metals and non-metals
  • Compounds have high melting/boiling points and can conduct electricity when molten or in solution
• Covalent bonding


  • Sharing of electrons between non-metals
  • Forms discrete molecules with relatively low melting/boiling points
• Giant covalent structures


  • Continuous networks of covalent bonds, e.g. diamond and graphite
• Total mass is conserved in chemical reactions
• Mole


  A specific number of atoms or molecules, used to compare amounts of substances
• One mole of a substance has a mass equal to its relative atomic or formula mass in grams
• Moleseqatio n


  Calculated as mass (g) divided by relative atomic/formula mass
• In a chemical reaction, the atoms that go in must come out, so we must balance equations
• Relative formula mass


  The sum of the relative atomic masses of the atoms in a compound
• Some reactions produce a gas product which, if it leaves the reaction vessel, will result in a seeming decrease in mass of the reactants
• Mole


  A specific number of atoms or molecules, used as a way of comparing amounts of substances
• One mole


  The amount of a substance that has a mass equal to its relative atomic or formula mass in grams
• In a balanced chemical equation, the ratio of moles of one substance to another is the stoichiometry
• The oxygen is the limiting reactant if there is not enough to react with all the methane
• Concentration of a solution

  Can be expressed in g per dm^3 or mol per dm^3
• One mole of HCl dissolved in 1 dm^3 of water makes hydrochloric acid with a concentration of 1 mol per dm^3
• Percentage yield is the amount of product actually made compared to the theoretical maximum
• One mole of any gas takes up a volume of 24 dm^3 at room temperature and pressure
• Reactivity series of metals

  • Hydrogen
  • Carbon
  • Most reactive metals
  • Least reactive metals
• A more reactive metal will displace a less reactive metal from a compound