Propane is a straight chain alkane that is heavier than air.

PROPANE is a colorless gas with a faint petroleum-like odor. It is shipped as a liquefied gas under its vapor pressure. For transportation it may be stenched. Contact with the unconfined liquid can cause frostbite by evaporative cooling. Easily ignited. The vapors are heavier than air and a flame can flash back to the source of leak very easily. The leak may be either a liquid or vapor leak. The vapors can asphyxiate by the displacement of air. Under prolonged exposure to fire or heat the containers may rupture violently and rocket.

Formula C3H8
Molecular weight 44.097 u
Hydrogen bond donors 0
Hydrogen bond acceptors 0
Percent composition
C 12.0107 u × 3 81.714 %
H 1.00794 u × 8 18.286 %

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National Center for Biotechnology Information. PubChem Database. Propane, CID=6334, (accessed on May 26, 2019)