The first three members of alkyne family — ethyne, propyne and butyne are colourless gases, the next eight members are liquids and the higher ones are solids. Except for ethyne, which has characteristic smell, all members are odourless.
The boiling point of alkynes increases with molar mass. Among hydrocarbons, alkynes have higher boiling point than alkenes and alkanes because of the presence of triple bond in alkynes.
Alkynes like alkanes and alkenes are non-polar; therefore, they are insoluble in water but readily dissolve in organic solvents such as ether, carbon tetrachloride and benzene.
The density of alkynes increases with mass. All alkynes are lighter than water.