Chlorine Chlorine is (at room temperature) a greenish-yellow gas that can be readily liquefied at 5170 Tarr or 6.8 atmospheres, at 20°C (68°F), and has a very disagreeable odor. Its element symbol is Cl, atomic number is 17, and atomic mass is 35.453. Chlorine’s melting point is —101° C or 149.8°F. The boiling point is -34.05°C or -29.29°F, at one atmosphere pressure. Chlorine is a member of the halogen group. Chlorine...

China Early China and Xia Dynasty: 10,000 BC to 1500 BC Chinese civilization started around 10,000 BC, when a group called the Yangshao (yahng show) settled near the Huang He River. Archaeologists have uncovered many Yangshao villages in northern China. In one village, they found the remains of farmhouses, built partly underground, with plaster floors, and roofs held up with wooden posts. About 3,000 BC, another farming group appeared the Lungshan...

Chihuahua Chihuahua is the largest state in Mexico, being nearly 250,000 square kilometer. The climate is dry to semi-arid but there is regular rainfall and occasionally extremes in temperature. The average temperature annually is 68 degree Fahrenheit. The state of Chihuahua has around 2.5 million residents. The highway system isn’t as vast as parts of the United States, but there is 11,000 kilometer of pave highways making links to the other...