CHEM-SEM1-'24-EXAM

• Thermal Conductivity

  A measure of how quickly heat flows from areas of higher heat to lower heat in a material
• Electrical Conductivity

  Requires the flow of charged particles between sources of electric potential difference
• Metals have free moving negatively charged electrons that conduct electricity
• Salts dissolved in water dissociate into ions that are free to move in solution and so solutions can also conduct electricity
• Electrical insulators are used to prevent unwanted flow of charge and PVC is commonly used to insulate electrical wires
• Aluminium is less dense than steel
• Expensive sporting equipment is made from carbon fibre due to its low density
• Elon (Space-X) exploits material properties of stainless steel for new rocket
• Differences in the properties of substances in a mixture can be used to separate them
• Methods to separate mixtures

  • Filtration
  • Distillation
  • Evaporation
• Physical properties used to separate mixtures

  • Size (sieve)
  • Magnetism
  • Density (introduce liquid)
• Separation methods for liquid/solid mixtures

  • Decant water off sand (density)
  • Filter sand from water (different phases)
  • Evaporate water from salt (boiling point)
• Separation methods for liquid/liquid mixtures

  • Decant for immiscible liquids (water and oil)
  • Fractional distillation for miscible liquids
• Sea water contains flora and fauna, 1 million bacteria per ml, 200 million viruses per ml, 35 g/L salt
• Adelaide Desalination plant can provide up to ½ Adelaide's water, has filtration stages to remove solids 3 mm, 0.1 mm, 0.04 μm and dissolved salts (reverse osmosis)
• Nanomaterials are substances that contain particles in the size range 1-100 nm
• Nanotechnology is an amalgamation of all sciences that exploit control at the atomic and molecular level
• Nanoparticles are materials with sizes between 1 and 100 nm
• Nanoparticles have a very high surface area to volume ratio and so have unusual properties
• Nanomaterial colour is often dependent on particle size
• Nanoparticles are smaller than the wavelength of visible light (400-700 nm) so are often transparent
• TiO2 nanoparticles can break down some chemicals when exposed to UV light
• Ferrofluid (magnetic nanoparticles suspended in liquid) can be applied to car suspension
• Nanostructures and wax on leaves repel water and oil (Lotus Effect)
• Silver nanoparticles can kill bacteria
• The size, shape and attached chemistry of gold nanoparticles can assist in targeting specific spots in the body
• Addition of nanoparticles to other materials can make them 'stick together' better, increasing hardness and toughness (nanocomposites)
• Clay nanoparticles make plastic strong enough and impermeable enough to be used in beer bottles
• Nanocomposites make very strong, lightweight materials for use in sport
• Year 11 starts by conducting a range of chemical reactions that introduce you to many of the topics we do this year
• Key Chemistry skills


  1. Observation

  2. Measuring

  3. Recording results

  4. Classifying products

  5. Inferring from data and making hypotheses
• Chemical change


  A new chemical substance with different chemical properties is formed in a chemical reaction
• Types of chemical reactions from last year

  • Gas given off
  • Colour change
  • Solid precipitated
  • Temperature changes
  • New odour appears
• Reaction of metal + acid

  Releases heat
• Reaction between two ionic solutions that results in a precipitate

  Precipitation reaction
• Reaction between an acid and a base

  Neutralisation reaction
• Reaction that requires heat from the surroundings

  Endothermic reaction
• Reaction of copper with zinc

  Redox reaction
• The uses of materials are related to their properties, including solubility, thermal and electrical conductivities, melting point and boiling point
• Properties of materials


  • Chemical
  • Physical