Figure 1. Space-filling model of a propane molecule. The black spheres represent carbon and the white spheres represent hydrogen[1]

Propane is an alkane with the chemical formula C3H8. As a type of hydrocarbon, it can undergo hydrocarbon combustion, which gives off heat. Propane is one of the hydrocarbon components of raw natural gas, which is a type of fossil fuel.[2] Propane is usually removed from natural gas before being shipped to customers, but is also sold separately as a fuel on its own.

Figure 2. A standard propane storage tank.[3]

Propane is normally in a gaseous state during consumption. However, it is normally stored as a liquefied propane gas in tanks such as the one shown in Figure 2. Propane has one of the highest energy densities (50.3 MJ/kg) of any hydrocarbon, second only to methane.[4]

Propane is a hydrocarbon commonly used in domestic settings. It is normally seen in appliances such as barbecues, patio heaters, and camping stoves.


Below is a table of some of the basic properties of propane.

Chemical formula C3H8
Molecular Mass 44.1 grams/mole
Energy density 50.3 MJ/kg[4]
Melting Point -190oC[5]
Boiling Point -42oC[5]

Combustion Reaction

Propane releases its chemical energy by undergoing hydrocarbon combustion. Below is a hydrocarbon combustion animation showing the net reaction that occurs when propane combines with oxygen.

C3H8 + 5O2 → 3CO2 + 4H2O + Heat Energy (Enthalpy)

The hydrocarbon combustion reaction releases heat energy and is an example of an exothermic reaction. The reaction also has a negative enthalpy change (ΔH) value.

For Further Reading


  1. Ben Mills. (2014, Dec. 12). Propane-3D-vdW-B [Online]. Available:
  2. “NATURAL GAS FAQs,” Pacific Northern Gas RSS. [Online]. Available: [Accessed: 24-May-2017]
  3. Personal photo submitted by a member of the Energy Education team.
  4. 4.0 4.1 (2014, Jul. 1). Chemical Potential Energy [Online]. Available:
  5. 5.0 5.1 (2015, Jan. 29). Boiling Points and Structures of Hydrocarbons [Online]. Available: [