chemistry paper 1

• Element


  The smallest part of an element that can exist and still be that element
• 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 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, using a stationary phase and a mobile phase
• Atom


  Consists of protons (positive particles) in the nucleus, neutrons (neutral particles) in the nucleus, and electrons (negative particles) in shells around the nucleus
• The average size of an atom is about 0.1 nanometers, 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 very small (about 1/1840 of a proton)
• 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
• Dalton model


  Atoms are indivisible, hard spheres
• Thomson (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


  • Elements are arranged in order of atomic number (number of protons)
  • Elements with similar properties are in vertical groups
• The periodic table used to be arranged by atomic weight, which had some issues, before being rearranged by atomic number
• Elements in the same group have the same number of electrons in their outer shell, which determines their chemical properties
• Electrons in outer shell


  Determines how an element reacts with other elements
• 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


  Molecules made of pairs of atoms, more reactive as you go up the group
• Noble gases


  Have a full outer shell, boiling points increase as you go down the group
• Metallic bonding involves regular rows of positive ions surrounded by a sea of delocalized electrons
• Alloys are mixtures of metals or a metal and carbon, where the different sized atoms distort the regular rows of positive ions
• Ionic bonding


  Occurs between a metal and a nonmetal, involves the transfer of electrons
• Ionic bonding


  1. Metal loses electron(s)

  2. Nonmetal gains electron(s)

  3. Positive and negative ions form a giant ionic lattice
• Covalent bonding


  Occurs between pairs of nonmetal atoms, where electrons are shared
• Types of covalent substances

  • Small covalent molecules
  • Giant covalent structures
• Small covalent molecules


  Tend to be gases or liquids at room temperature due to weak intermolecular forces
• Polymers


  Very long chains of repeating monomer units held together by covalent bonds
• 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