Y9: Environmental Chemistry

• What is meant by the term atmosphere?


  Mixture of gases surrounding a planet
• What is the proportion of nitrogen in the atmosphere?

  Around 80%
• What is the proportion of oxygen in the atmosphere?


  Around 20%
• What gases are present in the atmosphere in very small proportions?

  Water vapour, noble gases, carbon dioxide
• How has the percentage of carbon dioxide changed from the early atmosphere?


  Decreased
• How has the percentage of oxygen changed from the early atmosphere?

  Increased
• How has the percentage of nitrogen changed from the early atmosphere?

  Increased
• Why did oxygen levels in the atmosphere increase?


  Photosynthesis
• What two groups of living things caused oxygen levels in the atmosphere to increase?

  Algae and plants
• Give two ways in which nitrogen levels in the early atmosphere increased?

  Volcanoes, oxidation of ammonia
• Give three reasons why carbon dioxide levels in the early atmosphere decreased?


  Photosynthesis, dissolving in oceans, formation of sedimentary rocks and fossil fuels
• What are greenhouse gases?


  Gases in the atmosphere that can absorb infrared radiation (heat)
• What are the three main greenhouse gases?


  Carbon dioxide, water vapour and methane
• What is meant by the term greenhouse effect?


  "Trapping" of thermal energy within the atmosphere
• Why is the greenhouse effect important?


  Maintains global temperatures high enough for life
• What is global climate change?


  Changes in the Earth's weather patterns due to increased concentration of greenhouse gases
• What are four potential effects of global climate change?


  Increased global mean temperature, melting polar ice caps, rising sea levels, more frequent extreme weather events
• What is meant by the term carbon footprint?


  Total amount of greenhouse gases emitted over the life cycle of a product, service or event
• How can the carbon footprint be reduced?


  Reducing emissions of carbon dioxide and methane
• What is complete combustion?


  When a fuel burns in plenty of oxygen
• What are the products of the complete combustion of hydrocarbons?


  Carbon dioxide and water
• What do we use to test for the presence of water?


  Cobalt chloride paper
• What change is observed to cobalt chloride paper if water is present?

  Blue to pink
• What do we use to test for the presence of carbon dioxide?

  Bubble through limewater
• What change is observed to limewater if carbon dioxide is present?


  Turns cloudy
• What is incomplete combustion?

  When a fuel burns in a limited supply of oxygen
• What are the possible products of incomplete combustion of a hydrocarbon?

  Carbon dioxide, carbon monoxide, carbon (soot) and water
• Which pollutants may be released into the atmosphere when a fuel burns?

  Carbon dioxide, carbon monoxide, particulates, sulfur dioxide, oxides of nitrogen
• Why is carbon monoxide an environmental concern?

  Toxic
• Why is carbon monoxide difficult to detect?

  Colourless and odourless
• What environmental problem is caused by particulates?

  Global dimming
• What health problem is caused by sulfur dioxide and oxides of nitrogen?


  Respiratory problems
• What is crude oil?


  A fossil fuel formed from ancient plankton buried in mud
• What does crude oil consist of?

  A mixture of hydrocarbons with different carbon chain lengths
• Where is crude oil found?

  In underground reservoirs
• How is crude oil formed?


  High temperature and pressure over millions of years
• What is meant by the term fraction?


  A portion of crude oil in which the hydrocarbons have a similar number of carbon atoms
• What is the first step in fractional distillation in industry?


  Vaporisation
• What is the temperature gradient in the fractionating column?


  Cooler nearer the top
• How are the fractions of crude oil separated?


  According to their boiling temperature