Chemistry paper 1

• Element


  Different types of atoms represented in the periodic table by a symbol
• Compound


  Substance that contains two or more different types of atoms chemically bonded together
• Mixture


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


  Mixture of a solute (solid dissolved in a liquid) and a solvent
• Separation techniques


  1. Filtration (separate large insoluble particles from a liquid)

  2. Crystallization (evaporate solvent to leave behind solute)

  3. Distillation (separate liquids based on different boiling points)
• Physical change


  Change that does not involve the formation of new substances (melting, evaporation, etc.)
• Atom 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
• 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
• Periodic table


  Organises elements based on their properties
• Filling electron shells


  Shells fill up from the inside with a maximum of 2, 8, 8, 2 electrons
• Metals


  Elements to the left of the staircase on the periodic table, donate electrons
• Non-metals


  Elements to the right of the staircase on the periodic table, accept electrons
• Group


  Column an atom is in on the periodic table, indicates number of outer shell electrons
• Alkali metals


  Group 1 elements, have 1 outer shell electron
• Halogens


  Group 7 elements, have 7 outer shell electrons
• Noble gases


  Group 0 elements, have full outer shells
• Ion


  Atom that has gained or lost electrons, no longer electrically neutral
• Metallic bonding


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


  Bonding between a metal and a non-metal, involving the transfer of electrons
• Covalent bonding


  Bonding between non-metals, involving the sharing of electrons
• Molecular ion


  Ion formed from a group of atoms, e.g. hydroxide (OH-)
• Simple molecular/covalent structures


  Individual molecules that can mix together, have low boiling points
• Allotropes


  Different structural forms of the same element, e.g. diamond and graphite
• Mole


  Unit for measuring amount of substance, equal to Avogadro's number of particles
• Molar mass


  Mass of one mole of a substance, equal to its relative atomic/formula mass in grams
• Balancing equations


  Ensuring the number of atoms of each element is the same on both sides of the equation
• Relative formula mass


  The sum of the relative atomic masses of the atoms in a compound
• CO2 has a relative formula mass of 44 (12 + 2 x 16)
• Reactions producing a gas product

  Can result in a seeming decrease in mass of the reactants
• One mole of a substance has a mass equal to its relative atomic or formula mass in grams
• Moles


  Calculated as mass (g) divided by relative atomic or formula mass
• Balancing a chemical equation

  1. Determine the mole ratio of reactants and products

  2. Use mole ratios to calculate masses
• Methane combustion reaction


  • Requires 2 moles of oxygen per 1 mole of methane
• Calculating mass of product from mass of reactant

  1. Convert mass to moles

  2. Use mole ratios to find moles of product

  3. Convert moles of product to mass
• Stoichiometry


  The mole ratios of reactants and products in a balanced chemical equation
• Limiting reactant


  The reactant that is completely used up, limiting the amount of product formed
• Concentration of a solution

  Expressed in moles per cubic decimeter (mol/dm3)