paper 1

• Atom


  The smallest part of an element that can exist
• Element


  A substance of only one type of atom
• There are approximately 100 elements listed in the periodic table
• Groups of elements based on properties

  • Metals
  • Non-metals
• Compound


  Two or more elements combined chemically in fixed proportions which can be represented by formulae
• Compounds have different properties than their constituent elements
• Mixture


  Two or more elements or compounds not chemically combined together
• Mixtures have the same chemical properties as their constituent materials
• Methods to separate mixtures

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Separation methods for mixtures do not involve chemical reactions
• Simple distillation


  1. Liquid boils off and condenses in the condenser

  2. Thermometer reads the boiling point of the pure liquid
• Crystallisation/Evaporation


  1. Solution is heated until all the solvent evaporates

  2. Solids stay in the vessel

  3. Saturated solution is cooled to form crystals
• Fractional distillation


  1. Mixture of liquids with different boiling points are repeatedly condensed and vaporised in a fractionating column

  2. Liquids condense at different heights of the column
• Filtration


  1. Insoluble solid (residue) gets caught in the filter paper

  2. Filtrate is the substance that comes through the filter paper
• Chromatography


  Mixture dissolved in solvent is separated as the solvent rises up the paper
• Separating funnel


  Apparatus for separating immiscible liquids of different densities
• Plum-pudding model


  Atom is a ball of positive charge with negative electrons embedded in it
• Bohr/nuclear model


  Electrons orbit the nucleus at specific distances (shells), came from alpha scattering experiments
• Later experiments led to the discovery of protons in the nucleus
• James Chadwick's work provided evidence for the existence of neutrons in the nucleus
• Atom structure


  Small central nucleus (protons and neutrons) with electrons orbiting
• Protons and electrons have relative masses of 1, neutrons have a relative mass of 1, electrons have a very small mass
• Protons have a relative charge of 1, neutrons have a relative charge of 0, electrons have a relative charge of -1
• Atoms are electrically neutral because they have the same number of electrons and protons
• The radius of an atom is 0.1 nm
• The radius of a nucleus is 1 x 10-14 m, which is 1/10000 of the radius of the atom
• Number of protons in the nucleus

  Atomic number
• Atom radius


  0.1 nm
• Nucleus radius


  1 x 10-14 m, 1/10000 of the atom radius
• Atomic number


  The number of protons in the nucleus
• Atoms of the same element have the same number of protons in the nucleus
• The majority of an atom's mass is in the nucleus
• Mass number


  The total number of protons and neutrons
• Calculating number of neutrons


  Subtract atomic number from mass number
• Isotope


  Atoms of the same element with different numbers of neutrons, but same chemical properties
• Relative atomic mass


  The average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where the mass of 12C is 12
• Ion


  A charged particle formed when an atom loses or gains electrons
• Comparison of metal and non-metal properties

  • Boiling/melting point (high/low)
  • Conductivity (heat and electricity/don't conduct)
  • Appearance (shiny/dull)
  • Malleability (yes/brittle)
  • Density (high/low)
  • Oxides (basic/acidic)
• Reaction between metal and non-metal

  Forms an ionic compound
• Reaction between non-metal and non-metal

  Forms a molecular compound with covalent bonds