Earth's sunscreen – the ozone layer
Activity 3
Properties of chlorofluorocarbons (CFCs)
What are the properties of CFCs that made them so widely used when they were first introduced? Explain how some of these properties are related to the adverse effects of CFCs.
Teachers notes
CFCs are stable, non-flammable, low in toxicity, inexpensive to produce, and have a convenient boiling point and low critical pressure for liquification. The last two properties mean that CFCs are ideal for the cycle of evaporation and condensation involved in refrigeration and air conditioning.
Their low flammability and toxicity meant that there were few concerns about their use or escape. Their low cost and variety of uses meant that they were produced in large quantities. Because CFCs are stable, they remain indefinitely in the atmosphere and are gradually distributed around the Earth and into the stratosphere.
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Posted February 2007.