2018 specimen

• potable meaning

  safe to drink
• Why do you filter water to make it potable

  to remove undissolved solids
• A gas which bleaches litmus paper can be added to the water to make it potable

  The gas is chlorine, which sterilises water.
• Describe the difference between cracking and distillation

  Cracking involves a catalyst while distillation doesn't.
• The type of reaction is cracking

  decomposition
• conc of acid decreases

  Decrease in the number of particles so collisions are less frequent
• What is formulation

  designed as a useful product
• Explain how paper chromatography separates substances

  mobile phase/solvent moves through the paper and carries substances different distances, which depend on their attraction for the paper and the solvent .
• How to decrease the amount of carbon dioxide

  -used by plants and algae for photosynthesis

  -dissolved in the oceans

  -formed fossil fuels

  -limestone formation from carbonates
• Explain why sulfur dioxide has a low boiling point

  small molecules with weak intermolecular forces so only a small amount of energy is needed to separate the molecules .
• Q: A company stated: ‘A Life Cycle Assessment shows that using plastic bags has less environmental impact than using paper bags’.Evaluate this statement using Table 1. (6 marks)A (summarised):

  • Plastic bags are made from finite resources; paper bags are from renewable wood
  • However, paper bags use more energy, produce more waste, release more CO₂, and use far more water
  • Paper bags are biodegradable, and some CO₂ is offset by photosynthesis in trees
  • Overall, the data supports the idea that plastic bags may have less environmental impact
  • But it depends on disposal, recycling, and what factors are prioritised, so the conclusion could vary
• Q: Outline a plan to investigate how the rate of this reaction changed when the concentration of hydrochloric acid was changed.(6 marks)A (summarised):

  • Use a gas syringe to measure the volume of gas produced when magnesium reacts with hydrochloric acid
  • Add magnesium, start the timer, and record gas volume at regular intervals
  • Repeat the experiment with different acid concentrations
  • Keep variables like volume of acid, temperature, and magnesium mass/size the same
  • Ensure accurate timing and consistent methods to keep it a fair test
  • Compare how fast the gas is produced (rate of reaction) across concentrations
• Q: Carbon dioxide is a greenhouse gas.Describe the greenhouse effect. (4 marks)A:

  • Short wavelength radiation from the Sun passes through the Earth’s atmosphere and reaches the surface
  • The Earth’s surface absorbs the energy and re-emits it as longer wavelength infrared radiation
  • Greenhouse gases like carbon dioxide absorb this longer wavelength radiation
  • This trapped energy causes the temperature of the atmosphere to increase