topic 9; sep chem 2

• difference between synthetic and natural materials?

  • synthetic materials are manmade natural materials are made from nature 
• Why do nanoparticles have properties different from those same materials in bulk?

  • they have a high surface area to volume ratio and a high percentage of atoms are exposed at the surface
• how big are nanoparticles, fine particles, coarse particles?

  • nanoparticles - 1nm - 100nm
  • fine particles - 100nm - 2500nm
  • coarse particles - 2500nm - 10,000nm
• what are properties of nanoparticles?

  • high surface area to volume ratio
  • more reactive than materials with normal particle sizes
  • high proportion of their atoms or molecules at the surface of the particle
  • the use of nanoparticles instead of bulk material mean the smaller quantities are needed
• what are the uses of nanoparticles?

  • used in deodorants and face creams where they are absorbed deeper into the skin
  • used in sun creams as they’re better at blocking the suns rays that n normal-sized particles 
  • carbon nanocages are used to deliver drugs in the body
  • the large surface area makes them effective as catalysts
• what are the risks of using nanoparticles?

  • breathing in tiny particles could damage the lungs 
  • they could enter the bloodstream from their use in cosmetics with unpredictable effects on our cells
  • could enter the environment affecting aquatic life
• what is chemical analysis?

  • the instruments and methods we use to separate, identify and quantify different substances
• how do you test for chlorine?


  • fill the test tube with your sample gas 
  • dampen a piece of blue litmus paper
  • place the paper in the test tube
  • if chlorine is present the gas should bleach the paper so it turns white
  • might turn red at first as the chlorine dissolves in the water forming Hcl which is red on the pH scale
  • health and safety: wear a mask or do the experiment in a fume cupboard
• test for carbonates

  • add dilute hcl to the test sample
  • take the gas that's produced and run it through limewater (CO2 test)
  • if CO2 is present then so are the carbonates
• test for sulfates:

  • add dilute hcl
  • add barium chloride
  • if sulfate ions are present, barium sulfate (a white precipitate) will be formed
• flame tests

  • take a platinum or nichrome wire and clean it by dipping it in dilute hcl, rinsing it in distilled water, and then heating it over a bunsen burner flame
  • dip the wire into the compound you want to test
  • hold the wire in the clear blue flame
  • see what colour the flame turns as the compound burns
• what is the limitation of the flame test?

  if your sample contains more than one metal then the colour of the flames will mix together
• metal hydroxide test

  • react metal ions with sodium hydroxide to see what colour the solution turns
  • some metals produce coloured precipitates that determine the colour of the solution
• how does flame photometry work:

  • metal ions are heated until they emit light
  • the light is detected by the spectroscope which can distinguish between the individual wavelengths of light emitted
  • as each metal ion emits a unique combination of wavelengths, it will produce a unique line spectrum
  • this allows us to identify an unknown metal cation by comparing it to the line spectrums of those known metal cations
• drawbacks of instrumental methods

  they're more expensive than manual methods as they require more advanced technology
• addition polymerisation

  • large number of small monomers joined to create a large polymer
  • no other substances formed in the reaction:  A + B -> C
•  condensation polymerisation

  • any kind of polymer whose process involves a condensation reaction (products are water or methanol)
• what is a polyester made from?

  • a diol (an alcohol containing two -OH groups) and a dicarboxylic acid (a carboxylic acid containing two -COOH groups) 
• what are some properties of esters?

  • esters are volatile compounds (evaporate easily)
  • smell sweet or fruity so they are often used as flavourings in perfumes 
• what are the conditions needed for fermentation?

  • yeast - produces enzymes which break down the glucose molecules
  • temperature - at 37*C as enzymes work best
  • no oxygen - ensures the respiration is anaerobic as if oxygen is present the ethanol could oxidise to ethanoic acid (vinegar)
• low density polymers vs high density polymers 

  • both polymers are made from the same monomer, but they are made using different conditions
  • to change the properties of a polymer, we could change the reaction temperature, the reaction pressure or the catalyst
• what are thermosoftening polymers?

  • they melt when we heat them
  • we can reshape them while they are soft
  • they can go back to a solid when we cook them back down
• what happens when you heat thermosoftening polymers?

  • if we heat the polymer, the intermolecular forces break
  • now the polymer strands can separate from each other, and the polymer melts
  • if we cool the melted polymer, we reform the intermolecular forces so it goes back to a solid
• how do thermosetting polymers react to heat?

  • polymer chains are connected by strong cross-links
  • the strong crosslinks are not broken by heat which is why thermosetting polymers do not melt when heated
• polymers

  • they have very large molecules
  • they are made up of many small molecules that covalently bond to each other to form long chains
  • solid at room temperature due to strong intermolecular force
• what are the properties of alcohols?

  • flammable (so they can undergo complete combustion)
  • soluble (dissolves in water to form a solution with a neutral pH)
  • can be oxidised to form carboxylic acids 
• describe alkanes

  • form a homologous series (a group of organic compounds that react in a similar way)
  • same general formula
  • saturated - single carbon to carbon bonds
• describe the properties of alkanes

  • shorter chain = more volatile -> easier to evaporate (lower boiling point), more flammable
  • longer chain - higher bp, more viscous (thick, like honey)
• describe alkenes

  • unsaturated (double carbon to carbon bonds)
  • more reactive than alkanes
• define formulation

  • a mixture which has been designed as a useful product
  • e.g. fuel, cleaning products, paint