2019

• water that is safe to drink is called

  Potable
• test to see if the water is pure

  test-boil water

  result-boils at 100C
• Describe how oxides of nitrogen are produced in a car engine

  high temperature in the engine enables oxygen & nitrogen from the air to react.
• what is a formulation

  A mixture designed as a useful product.
• Explain how paper chromatography separates the dyes in a food colouring. (dont talk abt the experiment or how to do it )

  Dyes are distributed differently between the stationary phase and mobile phase so dyes move up the paper at different speeds.
• How to tell from the chromatogram that the food colouring contained more than one dye

  because the chromatogram has different colours in a vertical column
• 2 methods of extracting copper from low-grade ore

  -bioleaching

  -phytomining
• test for oxygen gas

  test-glowing splint

  result-relights
• Describe how crude oil is separated into fractions.

  Vaporise oil in a temperature gradient in column, vapour condense into fractions depending on the boiling point of the fraction
• why are Different products formed during the combustion of a hydrocarbon

  different amounts of oxygen available
• Describe a method to determine the mass of dissolved solids in a 100 cm³ sample of river water. (4 marks)A:

  • Weigh an empty container
  • Measure 100 cm³ of river water into the container
  • Heat the water until it has completely evaporated, leaving the solids behind
  • Weigh the container with the remaining solids
  • Subtract the initial mass of the container to find the mass of the dissolved solids
• Explain how the student could use chromatography to identify unknown dyes in the food colouring. (3 marks)A:

  • Run known dyes and the food colouring on the same chromatogram
  • Measure and calculate the Rf values for all the dyes
  • Compare the Rf values of the unknown dyes to those of the known dyes to identify any matches
• Copper is extracted from low-grade ores by phytomining.Describe how copper metal is produced by phytomining. (4 marks)A:

  • Plants are grown on low-grade copper ores
  • The plants absorb copper compounds from the soil
  • The plants are then harvested and burnt to produce ash
  • The ash is dissolved in acid to form a solution of copper compounds
  • Copper is then extracted from the solution by electrolysis
• How do the reaction profiles show that using a catalyst does not affect the overall energy change for the reaction?Tick (✓) one box. (1 mark)A: ✅ Both reaction profiles start at the same energy level and end at the same energy level.

  
• Suggest why producing ethanol from carbon dioxide is sustainable. (2 marks)A:

  • The amount of carbon dioxide used to produce ethanol is the same as the amount released when the ethanol is burned.
  • This means there is no net increase in carbon dioxide in the atmosphere.
• What is sustainable development? (2 marks)A:

  • Meeting the needs of the current generation
  • Without compromising the ability of future generations to meet their own needs
• Explain why the rate of this reaction changes.Give your answer in terms of collision theory. (3 marks)A:

  • The rate of reaction decreases because there are fewer acid particles as the reaction progresses
  • This leads to fewer frequent successful collisions between particles
  • The reaction eventually stops due to limiting factors, such as reactants being used up
• Carbon dioxide is a greenhouse gas.Describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter. (4 marks)A:

  • Short wavelength radiation from the Sun enters the Earth’s atmosphere
  • It is absorbed by the Earth’s surface and then re-emitted
  • The energy is re-emitted as longer wavelength infrared radiation
  • This longer wavelength radiation is trapped by greenhouse gases like carbon dioxide and methane, preventing it from escaping into space and warming the atmosphere