Chemistry Paper 1 - AQA

• Element


  The smallest part of an element that can exist and still be that element
• There are about a hundred different elements and they are shown in the periodic table
• Compound


  Formed when elements combine together in chemical reactions, contains two or more elements chemically combined in fixed proportions
• Naming compounds from their formula


  1. Take the name of the metal and leave it as it is

  2. Take the first syllable of the name of the nonmetal

  3. Add 'ide' on the end
• Naming compounds with three elements including oxygen


  1. Start the same as before

  2. Add the first syllable of the nonmetal

  3. Add 'ate' on the end
• Mixture


  Two or more elements or compounds that are not chemically combined together, they are not bonded
• Physical separation processes


  • Filtration
  • Crystallization
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Fractional distillation


  • Separates a mixture of liquids according to their boiling points
  • Uses a fractionating column with a temperature gradient
• Chromatography


  • Separates a mixture of liquids based on their solubility
  • Uses a stationary phase and a mobile phase
• Atom


  Smallest part of an element that can exist and still be that element, contains protons, neutrons and electrons
• The average size of an atom is about 0.1 nanometres, but the nucleus is only one ten-thousandth of the diameter of the atom
• The relative mass of an electron is not zero, it is about one over 1840
• Isotopes


  Atoms of the same element that have different numbers of neutrons
• Calculating the relative atomic mass of a sample with different isotopes


  1. Find the percentage of each isotope

  2. Multiply the mass of each isotope by its percentage

  3. Add the results together
• Atomic models


  • Dalton model - atoms are indivisible spheres
  • Thomson model - atoms have electrons embedded in a positive charge
  • Rutherford model - atoms have a tiny dense nucleus surrounded by electrons
  • Bohr model - electrons orbit the nucleus in distinct shells
  • Modern model - nucleus contains protons and neutrons
• Periodic table


  • Elements are arranged in order of atomic number (number of protons)
  • Elements with similar properties are in the same group (column)
  • The table has a periodic pattern due to the electron configuration of the elements
• The periodic table was originally arranged by atomic weight, which had some issues, before being rearranged by atomic number
• Electrons in outer shell


  Determines how an element reacts with other elements
• The periodic table hasn't always been laid out like this
• Initially, elements were arranged according to their atomic weight, which led to some problems
• Dmitri Mendeleev left gaps in the periodic table and made predictions about undiscovered elements, which turned out to be correct
• Metals


  Elements that will react to form positive ions
• Nonmetals


  Elements that will react but won't form positive ions
• Properties of metals


  • Form positive ions
  • Malleable
  • Conductive
  • High melting points
• Group 1 (alkali metals)


  Very reactive metals that react with water to produce hydrogen gas and a metal hydroxide
• Group 7 (halogens)


  Reactive elements that exist as diatomic molecules and can displace elements lower in the group
• Group 0 (noble gases)

  Stable elements with full outer shells, with boiling points increasing down the group
• Metallic bonding involves regular rows of positive ions surrounded by a sea of delocalized electrons
• Ionic bonding involves the transfer of electrons from a metal to a nonmetal, forming a giant ionic lattice
• Covalent bonding involves the sharing of electron pairs between nonmetal atoms, forming either small molecules or giant covalent structures
• Polymers


  Long chains of repeating monomer units held together by covalent bonds, with weak intermolecular forces between the chains
• Giant covalent structures are made up of thousands of atoms held together by strong covalent bonds
• Polymers


  Very long chains of repeating units called monomers
• Monomers


  Repeating units that are held together by strong covalent bonds to form a long chain
• Intermolecular forces


  Weak forces between one polymer chain and the next
• Intermolecular forces get quite big between long polymer chains, but are still nowhere near the size of ionic or covalent bonds
• Giant covalent structures


  Structures made up of thousands of atoms held together by strong covalent bonds
• Examples of giant covalent structures

  • Diamond
  • Graphite
  • Graphene
  • Fullerenes
  • Silicon dioxide
• Diamond


  • Every carbon atom makes four strong covalent bonds
  • Atoms can't slide over each other, making it incredibly hard
  • No delocalized electrons, so it can't conduct electricity
• Graphite


  • Every carbon atom makes three bonds, leaving one electron delocalized
  • Sheets of hexagons held together by weak intermolecular forces, allowing them to slide over each other
  • Can conduct electricity