Methane is a colorless, odorless, flammable gas with a suffocating odor. High pressure compressed gas in cylinders. Solubility: slightly soluble in water, soluble in alcohol and ether. , density (standard condition) 0.717 g / liter, boiling point -161.5 ℃, melting point -182.48 ℃. Combustion heat (kJ/mol): 889.5, critical temperature (°C): -82.6, critical pressure (MPa): 4.59. Flash point (°C): -188, ignition temperature (°C): 538. Under certain conditions, methane can undergo halogenation reaction (Cl2, Br2) and thermal decomposition (decomposition into C, H2, C2H2, etc.) and other reactions. When methane burns, the flame is bluish-white. The main component of biogas, pit gas and natural gas is methane. Methane in natural gas is liquefied at low temperature and under pressure, and can be transported across oceans by special ships. Chemical properties of methane Methane is stable and does not react with acidic KMnO4 solution or bromine water. A mixture of methane and air can explode when ignited. The explosion limit of methane in air is 5.3-14.0% (volume), and the explosion limit in oxygen is 5.4-59.2% (volume).

Applications of Methane
Methane is used as the standard fuel for the calorific value test of water heaters and gas furnaces
Methane is used in the production of standard gas and calibration gas for flammable gas alarms
Methane as a carbon source for solar cells, vapor chemical deposition of amorphous silicon films
Methane is used as a production raw material for pharmaceutical and chemical synthesis

Precautions 
Methane itself has no special toxic effect on the human body, but has an anesthetic effect when the concentration is high. When the content in the air is large, it can also cause hypoxia, suffocation, and cause poisoning symptoms. When the concentration of methane is greater than 10%, a feeling of pressure on the eyes and forehead occurs. When the concentration is higher, suffocation symptoms such as shortness of breath, fatigue, nausea, and vomiting begin to occur, and it can lead to loss of consciousness. When leaking gas, use forced ventilation to keep its concentration below the explosion range. If the leaking cylinder cannot be plugged, it should be moved to an open place and placed in the house, or an appropriate lamp holder should be installed to burn. Bottled gas products are high-pressure filling gas, which should be decompressed and depressurized before use. All the gas cylinders have an expiration date on them, and all expired gas cylinders must be sent to a department for safety inspection before they can continue to be used. When the exhaust gas of each bottle of gas is used, the residual pressure in the bottle should be kept at 0.5MPa, and the minimum residual pressure should not be lower than 0.25MPa. The bottle valve should be closed to ensure gas quality and safe use. Bottled gas products should be classified and stacked during transportation, storage and use. It is strictly forbidden to stack combustible gas and combustion-supporting gas together. It is not allowed to be close to open flames and heat sources. , Do not hit, it is strictly forbidden to start arc or arc on the gas cylinder, and it is strictly forbidden to load and unload it brutally.