How does a refrigerator work?

In the 1870s the German engineer Carl von Linde invented a continuous process of liquefying gases in large quantities, which led to his invention of the first efficient compressed-ammonia refrigerator. His revolutionary machine paved the way for the modern technology of refrigeration. Modern refrigerators run on ammonia gas, which liquefies when it is under high pressure using thermodynamics—a scientific law that says when two different temperatures of things touch or are near each other, the hotter surface cools and the colder surface warms up. Through the use of a compressor, small valves, and a coil, the liquid ammonia hits a low pressure, boils, and changes to a vaporizing gas. The coils go through the coldest part of the fridge, the freezer, as well as the main body of the refrigerator. The colder ammonia in the coil absorbs the heat out of the freezer and fridge, keeping the whole appliance cold. The compressor then takes back the ammonia gas and recycles it continuously. The thermometer inside the fridge regulates the temperature to make sure it is always the same.