Human activity has caused changes in the composition and the structure of the atmosphere. Chemists monitor these changes so that further damage can be limited
Students learn to:
- describe the composition and layered structure of the atmosphere
- identify the main pollutants found in the lower atmosphere and their sources
- describe ozone as a molecule able to act both as an upper atmosphere UV radiation shield and a lower atmosphere pollutant
- describe the formation of a coordinate covalent bond
- demonstrate the formation of coordinate covalent bonds using Lewis electron dot structures
- compare the properties of the oxygen allotropes O2 and O3 and account for them on the basis of molecular structure and bonding
- compare the properties of the gaseous forms of oxygen and the oxygen free radical
- identify the origins of chlorofluorocarbons (CFCs) and halons in the atmosphere
- identify and name examples of isomers (excluding geometrical and optical) of haloalkanes up to eight carbon atoms
- discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems
- analyse the information available that indicates changes in atmospheric ozone concentrations, describe the changes observed and explain how this information was obtained
Students:
- present information from secondary sources to write the equations to show the reactions involving CFCs and ozone to demonstrate the removal of ozone from the atmosphere
- gather, process and present information from secondary sources including simulations, molecular model kits or pictorial representations to model isomers of haloalkanes
- present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs