1. Refrigerators Lizmayling Roa

2. Why are they so important? • Keep your food cold and fresh. • Without food you can’t live. • Melted ice cream doesn’t taste as good. • You want to eat spoiled milk with your fruity pebbles? • I didn’t think so.

3. Historic Info • Since the mid- 1800's, refrigerators have been widely used to keep food from spoiling. • In 1805, Oliver Evans, designed the first refrigeration machine. • Refrigeration is not a natural process. • According to the second law of thermodynamics, all processes involving the transfer of heat move it from the hotter body to the colder body,

4. How does it work? • A gas cools on expansion. • When you have two things that are different temperatures that touch or are near each other, the hotter surface cools and the colder surface warms up. This is a law of physics called the Second Law of Thermodynamics

6. Why is your fridge running? • Chloro-Flouro-Carbon or CFC • This gas was found to hurt the environment if it leaks from refrigerators. So now, other chemicals are used in a slightly different process. • Modern refrigerators don't use CFC. • HFC-134a, also called tetrafluoroethane. • HFC turns into a liquid when it is cooled to -15.9 degrees Fahrenheit (-26.6 degrees Celsius).