The Chemical Makeup of Propane

Propane has many wonderful uses for your home and business. As a widely-used and rapidly-growing energy source, propane, also known as liquefied petroleum gas, is a safe, clean-burning fuel that is economical and easy to transport. Here at Tri Gas & Oil, we are proud to bring this great fuel to your homes and businesses. The story of propane begins long before it reaches your home tank or work equipment. Propane, a natural gas component, formed over millions of years. Propane’s chemical makeup — C3H8 — comes from three carbon molecules bonding with eight hydrogen atoms. 

The organic classification originates from propane’s carbon structure. One of the essential nuggets regarding propane comes with its non-polar designation, which means it won’t mix polar substances such as water. Remember when your science teacher said, “Oil and water don’t mix,” well, the same goes for propane and water. They won’t mix either. 

Being a type of hydrocarbon, propane falls in the Alkane class, which are molecules joined with single covalent bonds. Methane, known as natural gas, is the simplest alkane because one carbon atom is bonded to four hydrogen atoms. Ethane’s two carbon atoms are bonded together, and each is bonded to three hydrogen atoms to make a total of six hydrogen atoms. To make propane, it develops a chain of three carbon atoms bonded with a total of eight hydrogen atoms. Butane, commonly used for hand-held torches, contains four carbon atoms with 10 hydrogen atoms.

Propane features a more direct makeup as a straight-chain alkane. With eight total hydrogen bonds, the outer carbon atoms join three hydrogen atoms, each while the middle carbon atom bonds with just two hydrogen atoms.

Propane only can be stored in a liquid state when in a pressurized tank because its boiling point is -44 degrees Fahrenheit. The common propane uses include powering furnaces, hot water heaters, outdoor gas grills, gas-powered camping cooking stoves, forklifts, farm irrigation machines, fleet vehicles, and even buses.

The Science Behind the 80/20 Rule

Have you ever looked at your propane tank gauge and wondered why your tank at home never seems completely full?

Your local propane supplier wants you to know there is a good reason for this, and it has a lot to do with safety. In case you were curious, there is some fascinating science behind it as well. 

Propane tanks are only filled to 80% of their capacity, leaving 20% of your tank empty. This preventative measure is called the 80/20 Rule, and it acts as a safeguard against the changing temperatures — and the resulting increase of volume — inside of your propane tank.

As propane gets hotter, it expands. Water does the same thing as it heats up. However, propane will increase in volume almost 17 times greater than water. That’s a whole lot of expansion! All of that extra liquid needs somewhere to go, and that is why we only fill tanks to 80% capacity. This empty space is a buffer against the pressure that builds up when your tank gets hot. 

Safety always comes first for Tri Gas & Oil, and now you know the science behind this procedure too! Whether you are enjoying a toasty house with your propane fireplace in winter or a delicious cookout in summer, propane is a safe and economical option, all year long.


  • TriGas & Oil Co, Fuel Oil, Federalsburg, MD