The chemical reaction for CFC is: CCl3F = CCl2F + Cl. Uses. Due to their chemical properties, CFCs became useful as coolants and propellants. More commonly known as freon for refrigeration, CFCs are used extensively in appliances as a safe method of refrigeration. The other main use for CFCs has been as a propellant for aerosol cans.
The earliest known Egyptian pyramids are found at Saqqara, northwest of Memphis. The earliest among these is the Pyramid of Djoser (constructed 2630 BCâ2611 BC) which was built during the third dynasty. This pyramid and its surrounding complex were designed by the architect Imhotep, and are generally considered to be the world's oldest monumental structures constructed of dressed masonry.
The ancient Egyptians built large and elaborate pyramids as tombs for their kings, the pharaohs. They were built of huge stone blocks and took a couple of decades to build. The three pyramids of Giza are the most famous. They were built in the 26th century B.C. The largest pyramid of Giza is called the Great Pyramid of Khufu. It is also the largest and grandest pyramid ever built. It is 479 feet tall (146 meters). The pharaoh Sneferu built this pyramid for his son, Khufu, in 2540 B.C. It was built from millions of blocks of limestone and granite.