chemistry paper 2

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    • What is potable water?
      Water that's safe for humans to drink
    • Why do chemists not consider potable water pure?
      It contains dissolved substances besides H₂O
    • What are the acceptable pH levels for potable water?
      Between 6.5 and 8.5
    • What must not be present in potable water?
      Bacteria or other harmful microbes
    • What is fresh water?
      Water with low levels of dissolved substances
    • How does rainwater collect as surface water?
      In lakes, rivers, and reservoirs
    • What is the primary source of domestic water in warm areas of the UK?
      Groundwater
    • What is the first step in treating fresh water?
      Filtration to remove large particles
    • What are the steps involved in treating fresh water?
      1. Filtration
      • Wire mesh screens out large debris
      • Gravel and sand filter out solids
      1. Sterilization
      • Kills harmful bacteria and microbes
      • Methods: chlorine gas, ozone, ultraviolet light
    • What is desalination?
      Treating seawater to produce potable water
    • How can seawater be desalinated?
      By distillation or reverse osmosis
    • What is the purpose of adding fluoride to water?
      To promote dental health
    • Why is the addition of fluoride controversial?
      People have no choice over its consumption
    • What is the first step in testing water's pH?
      Using a pH meter
    • How can sodium ions be tested in water?
      By performing a flame test
    • What indicates the presence of chloride ions in water?
      A white precipitate forms with silver nitrate
    • What happens during the distillation of salty water?
      Water boils, leaving salts behind
    • What is the purpose of the condenser in distillation?
      To condense steam back into liquid water
    • What is reverse osmosis?
      A process using membranes to filter water
    • Why are distillation and reverse osmosis expensive?
      They require a lot of energy
    • What is waste water?
      Water used for various domestic purposes
    • What happens to waste water from homes?
      It goes to sewage treatment plants
    • What types of waste water come from agriculture?
      Nutrient run-off and slurry
    • Why must sewage be treated before release?
      To remove organic matter and harmful microbes
    • What is the Haber Process?
      An industrial process producing waste water
    • What are the stages of sewage treatment?
      1. Screening
      • Removes large materials and grit
      1. Sedimentation
      • Heavier solids sink to form sludge
      1. Aerobic digestion
      • Air is pumped to encourage bacteria
      1. Anaerobic digestion
      • Breaks down sludge, releasing methane
    • What is the purpose of anaerobic digestion in sewage treatment?
      To break down sludge and produce methane
    • What can methane gas from anaerobic digestion be used for?
      As an energy source
    • What additional treatments may be needed for toxic waste water?
      Adding chemicals, UV radiation, or membranes
    • Why is sewage treatment more energy-efficient than desalination?
      It requires fewer processes and less energy
    • What is a common concern about drinking recycled sewage water?
      People dislike the idea of it
    • What is required for particles to react according to collision theory?
      Particles must collide with enough energy
    • What does the collision frequency refer to?
      How often reacting particles collide
    • How does doubling the collision frequency affect the reaction rate?
      It doubles the rate of the reaction
    • What is the minimum energy needed for particles to react called?
      Activation energy
    • How can the rate of reaction be increased according to the study material?
      By increasing collisions or energy of particles
    • What factors affect the rate of reaction?
      • Temperature
      • Concentration of solution or pressure of gas
      • Surface area of solid reactants
      • Presence of a catalyst
    • How does increasing temperature affect reaction rates?
      Particles move faster and collide more frequently
    • What happens when the concentration of a solution is increased?
      More particles are present in the same volume
    • How does increasing surface area affect reaction rates?
      More area allows for more frequent collisions
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