1. Physical State
The first three alkynes are gases while those containing five to thirteen carbon atoms are liquids and higher alkynes are solids.
2. Melting and Boiling Points
The melting and boiling points of alkynes are quite low and increase regularly with increase in molecular mass. Alkynes are less volatile than alkanes and alkenes.
Alkynes are insoluble in water but are soluble in organic solvents such as benzene, hexane, ether, carbon tetrachloride, etc.
All alkynes are lighter than water. Their densities increase regularly with increase in molecular mass.
The physical properties of some alkynes are listed in Table 42.1.
Table 42.1. Physical Properties of Some Alkynes