Which of the following is NOT a characteristic of alkynes?

Alkynes are defined as hydrocarbons that contain at least one carbon-carbon triple bond. This triple bond significantly influences their chemical and physical properties. The presence of the triple bond is why the first two characteristics listed—having a triple bond and having a linear geometry—are true for alkynes. The linear geometry results from the sp hybridization of the carbon atoms involved in the triple bond.

When it comes to boiling points, alkynes typically exhibit higher boiling points compared to alkanes of similar molecular size. This is due to the stronger intermolecular forces present in alkynes attributed to their triple bonds, which require more energy to break during the phase change from liquid to gas.

The statement that alkynes are saturated hydrocarbons is not true. Saturated hydrocarbons contain only single bonds and are fully "saturated" with hydrogen. Alkynes, on the other hand, are considered unsaturated because they contain a triple bond, which means they can react with additional hydrogen atoms or other substituents. Thus, the characteristic of being a saturated hydrocarbon does not apply to alkynes.