Chalk

Alkynes are colorless and insoluble in water. The lower the members of alkynes (acetylene, allylene, and crotonylene) are gases. The homology from carbon number 5 to 15 (C5H8 to C15 H28) are liquid and the higher members are solid. Acetylene possesses a pleasant odor when pure. The impure acetylene contains phosphine, hydrogen sulphide etc and hence smells bad. Acetylene can be liqiufied at 0°C under 48 Torrs of pressure. The melting point of Acetylene is -81.8°C and boiling point -83.4°C. It is slightly soluble in water but highly soluble in organic solvents like alcohol and acetone. Acetylene under suitable conditions decomposes with evolution of a lot of heat and sudden increase in volume, which causes explosion. Hence liquid acetylene is highly explosive.

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Uses
Acetylene is used in  Illumination of cycle lamps, hawker's lamps and buoys in light houses.  Producing oxyacetylene flame for welding and cutting of iron and steel.  Artificial ripening of fruits and vegetables.  The manufacture of Hydrogen.  The manufature of plastics and a number of other organic compounds.
Alkynes are generally used as the starting materials for the manufacture of a large number of organic compounds of industrial importance such as, chloroprene, vinyl chloride etc.
Uses of Alkyne Assignment Help

Aliphatic hydrocarbons with one triple bond between carbons are called alkynes. They follow the naming convention of the alkanes except that the suffix -yne is used instead of -ane. For alkynes above propyne the position of the double bond must be specified in the name.
Alkynes are unsaturated hydrocarbons and are generally very reactive. Typical reactions involve the addition of hydrogens or halogens.
Alkynes are hydrocarbons that contain a carbon–carbon triple bond. Because of its triple bond, an alkyne has four fewer hydrogens than the corresponding alkane. Therefore, the