c1-5

• Element


  Substance made from only one type of atom
• Compound


  Substance made from two or more different types of atoms chemically bonded together
• Mixture


  Two or more different elements or compounds that are not chemically bonded together
• Balancing chemical equation


  1. Can't change the little numbers

  2. Balance phosphorus by putting 2 on the right

  3. Balance oxygen by putting 3 in front of O2 on the left
• Distillation to get pure water from salt water

  1. Heat solution so water (solvent) evaporates

  2. Use condenser to turn water vapour back into liquid, leaving salt (solute) behind
• Solid


  • Particles vibrate about fixed positions, tightly packed, cannot be compressed
• Liquid


  • Particles free to move past each other, still touching, cannot be compressed
• Gas


  • Particles move with fast speeds, high kinetic energy, far apart, can be compressed
• Rutherford discovered that atoms are mostly empty space with a small, positive charge in the middle (nucleus)
• Subatomic particles


  • Protons (positive charge, relatively same mass as neutrons)
  • Neutrons (neutral charge, relatively same mass as protons)
  • Electrons (negative charge, very small mass)
• Atomic number


  Number of protons in the atom's nucleus
• Mass number (relative atomic mass)


  Number of protons plus neutrons in the nucleus
• Electron filling of shells in atoms up to calcium

  1. First shell max 2 electrons

  2. Second shell max 8 electrons

  3. Etc.
• Ionic bonding


  Metals donate their outer electrons to non-metals, leaving them with a positive charge (ions)
• Covalent bonding


  Non-metals share electrons to get a full outer shell
• Reactivity groups


  • Group 1 (alkali metals, most reactive)
  • Group 7 (halogens, get more reactive up the group)
  • Group 0 (noble gases, very unreactive)
• Metallic bonding


  Metal atoms form a lattice with a 'sea' of delocalized electrons, making them good conductors
• Formula for iron(III) oxide is Fe2O3
• Structural formula


  Lines represent covalent bonds
• Dot and cross diagram


  Dots and crosses represent shared electron pairs in covalent bonds
• Ionic compounds


  • High melting points, can only conduct electricity when molten or dissolved
• Simple covalent compounds


  • Relatively low melting and boiling points, cannot conduct electricity
• Graphite can conduct electricity, diamond cannot, even though both are giant covalent structures of carbon
• Relative formula mass (RAM)

  Sum of the relative atomic masses of the atoms in a compound
• Calculating moles of a compound

  Moles = mass / RAM
• Calculating mass of water needed to make magnesium hydroxide


  1. Use balanced equation to find mole ratio

  2. Moles of water = 2 x moles of magnesium hydroxide

  3. Mass of water = moles of water x RAM of water
• Limiting reactant


  The reactant that runs out first in a reaction
• Calculating concentration of a solution

  1. Concentration = moles / volume

  2. Rearrange to find moles = concentration x volume
• Percentage yield


  Actual mass of product / Theoretical mass of product x 100
• Atom economy


  Mass of desired product / Total mass of reactants x 100
• Displacement reaction


  More reactive metal or non-metal takes the place of a less reactive one in a compound
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• pH


  Measure of H+ ion concentration, below 7 is acidic, above 7 is alkaline
• Neutralising an acid with an alkali


  1. Moles of alkali = 2 x moles of acid

  2. Products are a salt and water
• Electrolysis


  • Positive ions (cations) attracted to cathode, reduced
  • Negative ions (anions) attracted to anode, oxidised
• In electrolysis, more reactive metals stay in solution, hydrogen is produced at cathode
• Exothermic reaction


  Potential energy decreases, kinetic energy (temperature) increases
• Endothermic reaction


  Total bond energies of reactants > total bond energies of products, so energy is absorbed