Chlorofluorocarbon: Chlorofluorocarbon (CFC), any of several organic compounds composed of carbon, fluorine, and chlorine. When CFCs also contain hydrogen in place of one or more chlorines, they are called hydrochlorofluorocarbons, or HCFCs. CFCs are also called Freons, a trademark of the E.I. du Pont de Nemours & Company in Wilmington, Del. CFCs were originally developed as refrigerants during the 1930s. Some of these compounds, especially trichlorofluoromethane (CFC-11) and dichlorodifluoromethane (CFC-12), found use as aerosol-spray propellants, solvents, and foam-blowing agents.
The Egyptians started building the Great Pyramid of Giza on August 23, 2470 B.C., according to controversial new research that attempts to place an exact date on the start of the ancient construction project. Enlarge Photo. Printer Friendly. Email to a Friend.
The great pyramids of Giza were built during the times when Khufu was the pharaoh. He ruled over Egyptâ¦ from 2551 BC to 2528 BC. Khufu had built the pyramids during 2560 BC. The pyramids took a period of more than 20 years to get complete from 2550 to 2530 BC and served as a tomb when Khufu died. Find more info at the link below.