SCI Revision T3

• Law Of Conservation Of Energy


  Energy can not be created or destroyed, Energy may change forms, but the total amount of energy remains the same
• Efficiency


  During energy conversions, some energy is often lost as thermal energy (heat) due to friction or other resistances, making the process less efficient
• Ohm's Law


  At constant temperature, the current flowing through a conductor between two points is directly proportional to the voltage across those same points
• Voltage & Current


  Are directly proportional which means that when voltage goes up the current does too. Similarly, when voltage goes down the current does too. The formula is: V = I R
• Current & Resistance


  Are inversely related which means that when one increases the other decreases. The formula is: I = VR
• Energy Forms


  • Kinetic Energy
  • Potential Energy
  • Thermal Energy
  • Chemical Energy
  • Electrical Energy
  • Light (Radiant) Energy
  • Sound Energy
  • Nuclear Energy
• Energy Changes


  1. Chemical to Thermal and Light

  2. Electrical to Light and Thermal

  3. Kinetic to Potential

  4. Potential to Kinetic

  5. Mechanical to Electrical

  6. Electrical to Mechanical
• Examples in Everyday Life

  • Eating Food: Chemical → Kinetic → Thermal
  • Driving a Car: Chemical → Kinetic → Thermal & Sound
  • Photosynthesis: Light → Chemical
• The Ozone Layer


  A region of Earth's stratosphere that contains a high concentration of ozone (O3) molecules, Located 10-30 kilometres above the Earth's surface, Absorbs the majority of the Sun's harmful UV radiation, Prevents UV radiation from reaching Earth's surface
• Types of Ultraviolet (UV) Rays

  • UVA
  • UVB
  • UVC
• Chlorofluorocarbons (CFCs)


  Man-made chemical compounds, once used in refrigeration, air conditioning, and aerosol sprays, composed of chlorine, fluorine, and carbon atoms
• Effect of CFCs on the Ozone Layer

  1. UV Radiation Breakdown

  2. Chlorine and Ozone Reaction

  3. Chlorine Cycle
• 1974: Mario Molina and Sherwood Rowland's research links chlorofluorocarbons (CFCs) to ozone depletion, raising awareness about potential dangers to the ozone layer


  1970s
• • 1985: British Antarctic Survey scientists Joe Farman, Brian Gardiner, and Jonathan Shanklin published a paper revealing the severe depletion of ozone over Antarctica, later known as the "ozone hole"
  • 1987: The Montreal Protocol, an international treaty, aims to phase out the production and consumption of ozone-depleting substances, including CFCs and related chemicals


  1980s
• • 1990: The London Amendment to the Montreal Protocol has been accepted, which adds stricter controls and increases the list of restricted chemicals
  • 1992: The Copenhagen Amendment further tightens controls and accelerates the phase-out of ODS (ozone-depleting substances)
  • 1995: Mario Molina, Sherwood Rowland, and Paul Crutzen were awarded the Nobel Prize in Chemistry for their groundbreaking work on atmospheric chemistry, specifically in the study of ozone formation and decomposition

  1990s
• • 2000: The ozone hole reaches its largest recorded size, covering approximately 29.9 million square kilometres
  • 2002: Scientists observe an unexpected temporary healing of the ozone hole, providing hope and confirming the effectiveness of the Montreal Protocol


  2000s
• • 2010: The production of most ODS is completely phased out following the Montreal Protocol
  • 2014: NASA confirms that the ozone hole is starting to recover, demonstrating the positive impact of the global reduction in ODS
  • 2016: The Kigali Amendment to the Montreal Protocol is adopted, targeting the phase-down of hydrofluorocarbons (HFCs), which are potent greenhouse gases but not ozone-depleting substances

  2010s
• • 2020: The ozone hole over Antarctica is the smallest it has been since its discovery, thanks to the Montreal Protocol's success and unusual weather patterns
  • 2021: A Nature study indicates that the ozone layer is expected to return to 1980 levels by the mid-21st century, assuming current regulations are upheld

  2020s
• What lessons were learned from the Montreal Protocol's success in curbing ozone depletion and how can we apply them to global climate change?