Chemistry paper 1 (C 1-5)

• Elements


  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
• Compounds


  Formed when elements combine together in chemical reactions, contain two or more elements chemically combined in fixed proportions
• Fixed proportions


  Always the same ratio of elements
• Naming compounds from formula

  1. Take name of metal as is

  2. Take first syllable of nonmetal

  3. Add 'ide' for ionic compounds

  4. Add 'ate' if oxygen is present
• Mixture


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


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


  Use a funnel and filter paper to separate an insoluble solid from a liquid
• Crystallization


  Use an evaporating basin and heat to remove liquid and leave behind a solid
• Simple distillation


  Use heating and cooling to separate a liquid mixture
• Fractional distillation


  Use a fractionating column and temperature gradient to separate a mixture of liquids by boiling point
• Chromatography


  Use a stationary phase (paper) and mobile phase (solvent) to separate a mixture of liquids based on solubility
• Atom


  Smallest part of an element that can exist and still be that element, contains protons, neutrons and electrons
• Parts of an atom

  • Protons (positive)
  • Neutrons (neutral)
  • Electrons (negative)
• Average size of an atom is about 0.1 nanometres, but the nucleus is only one ten-thousandth of the diameter of the atom
• Electrons have a very small mass, not zero
• Isotopes


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

  Work out percentage of each isotope and multiply by its mass, then add together
• Dalton model


  Atoms are indivisible spheres
• Plum pudding model


  Atoms have a positive charge with electrons embedded in it
• Rutherford model


  Atoms have a tiny dense positive nucleus surrounded by empty space with electrons orbiting
• Bohr model


  Electrons orbit the nucleus in distinct shells at different energy levels
• Periodic table


  Arranged in order of atomic number (number of protons), elements with similar properties are in the same group
• The periodic table used to be arranged by atomic weight, which had some issues like putting reactive metals next to noble gases
• 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
• Metals


  • Malleable
  • Conductive
  • High melting points
• Groups in the periodic table

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


  Very reactive, float on water, produce hydrogen gas, can produce coloured flames
• Halogens


  Group 7 elements, consist of molecules made of pairs of atoms, get more reactive as you go up the group
• Noble gases


  Group 0 elements, have a full outer shell, boiling points increase as you go down the group
• The next unit is about chemical bonds: metallic, ionic, and covalent
• Metallic bonding


  Positive ions in a sea of delocalized electrons, held together by strong electrostatic forces, makes metals malleable and conductive
• Alloys


  Mixtures of metals or a metal and carbon, distorted structure makes them harder than pure metals
• Ionic bonding


  Occurs between a metal and a nonmetal, involves the transfer of electrons, forms a giant ionic lattice held together by strong electrostatic forces
• Covalent bonding


  Occurs between pairs of nonmetal atoms, where they share one or more pairs of electrons