Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Ethylene - Thermophysical Properties

Sponsored Links

Ethylene, C2H4, is a highly flammable, colorless and noncorrosive gas with a sweet odor. It is easily ignited and a flame can easily flash back to the source of the leak. Under prolonged exposure to fire or heat the containers may rupture violently and rocket. Can cause explosion. Vapors arising from the boiling liquid are lighter than air. Ethylene is not toxic, but is a simple asphyxiant.

Ethylene is used as an anesthetic, a refrigerant, and to make other chemicals as polymers and plastics.

Ethylene is produced in petrochemical processes, as steam cracking  where hydrocarbons and steam are heated to 750–950 °C. This process converts large hydrocarbons into smaller ones and introduces unsaturated products.

The phase diagram of ethylene is shown below the table.

Chemical, physical and thermal properties of ethylene:
Values are given for gas phase at 25oC /77oF / 298 K and 1 bara, if not other phase, temperature or pressure given.

For full table with Imperial Units - rotate the screen!

Property Value Unit Value Unit Value Unit Value Unit
Autoignition temperature 723 K 450 °C 842 °F
Boiling Point 169 K -104 °C -155 °F
Critical density 7.63 mol/dm3 214 kg/m3 0.415 slug/ft3 13.4 lb/ft3
Critical pressure 5.06 MPa=MN/m2 50.6 bar 49.9 atm 734 psi=lbf/in2
Critical temperature 282.4 K 9.2 °C 48.6 °F
Critical volume 131 cm3/mol 0.00467 m3/kg 2.41 ft3/slug 0.0748 ft3/lb
Density 40.6 mol/m3 1.138 kg/m3 0.00221 slug/ft3 0.07104 lb/ft3
Density (liquid) at -104 °C/-155°F 20567 mol/m3 577 kg/m3 1.12 slug/ft3 36.0 lb/ft3
Flammable, gas and liquid yes highly
Flash point 137 K -136 °C -213 °F
Gas constant, individual, R 296.4 J/kg K 0.0823 Wh/(kg K) 1772 [ft lbf/slug °R] 55.08 [ft lbf/lb °R]
Gibbs free energy of formation (gas) 68 kJ/mol 2424 kJ/kg 1042 Btu/lb
Heat (enthalpy) of combustion (gas) -1411 kJ/mol -50303 kJ/kg -21626 Btu/lb
Heat (enthalpy) of formation (gas) 52.4 kJ/mol 1868 kJ/kg 803 Btu/lb
Heat (enthalpy) of evaporation at -104°C/-155°F 13.6 kJ/mol 483 kJ/kg 207.7 Btu/lb
Heat capacity, Cp (gas) 42.9 J/mol K 1.53 kJ/kg K 0.365 Btu/lb°F or cal/g K
Heat capacity, Cp (liquid) at -104°C/-155°F 67.4 J/mol K 2.40 kJ/kg K 0.574 Btu/lb°F or cal/g K
Heat capacity, Cv (gas) 34.6 J/mol K 1.24 kJ/kg K 0.295 Btu/lb°F or cal/g K
Heat capacity, Cv (liquid) at -104°C/-155°F 38.7 J/mol K 1.38 kJ/kg K 0.330 Btu/lb°F or cal/g K
Ionization potential 10.5 eV
log KOW (Octanol/Water Partition Coefficient) 1.13
Melting point 104.15 K -169.0 °C -272.2 °F
Molecular Weight 28.054 g/mol 0.06185 lb/mol
Solubility in water, at 25°C 0.131 mg/ml
Sound velocity 330 m/s 1082 ft/s 739 mi/h
Specific Gravity (gas) (relativ to air) 0.978
Specific Heat Ratio (gas) - CP/CV 1.24
Specific Heat Ratio (liquid) - CP/CV 1.74
Specific Volume 0.0247 m3/mol 0.879 m3/kg 453 ft3/slug 14.1 ft3/lb
Standard molar entropy, S° (gas) 219.32 J/mol K 7.82 kJ/kg K 1.87 Btu/lb °F
Standard molar entropy, S° (liquid) 117.8 J/mol K 4.20 kJ/kg K 1.00 Btu/lb °F
Surface tension at -104°C/-155°F 16.00 dynes/cm 0.016 N/m
Thermal Conductivity 0.020 W/m°C 0.0118 Btu/hr ft °F
Triple point pressure 0.000122 MPa=MN/m2 0.00122 bar 0.00120 atm 0.0177 psi=lbf/in2
Triple point temperature 104.0 K -169.16 °C -272.49 °F
Vapor (saturation) pressure 6.9449 MPa=MN/m2 5.21E+04 mm Hg 68.543 atm 1007.30 psi=lbf/in2
Viscosity, dynamic (absolute) 0.0103 cP 6.9 [lbm /ft s*10-6] 0.22 [lbf s/ft2 *10-6]
Viscosity, kinematic 9.05 cSt 97.4 [ft2/s*10-6]

Back to top

Follow the links below to get values for the listed properties of ethylene at varying pressure and temperature:

See also more about atmospheric pressure, and STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure,
as well as Thermophysical properties of:
Acetone, Acetylene, Air, Ammonia, Argon, Benzene, Butane, Carbon dioxide, Carbon monoxide, Ethane, Ethanol, Helium, Hydrogen, Hydrogen sulfide, Methane, Methanol, Nitrogen, Oxygen, Pentane, Propane, Toluene, Water and Heavy water, D2O.

Ethylene is a gas at standard conditions. However, at low temperature and/or high pressures the gas becomes a liquid or a solid.

The ethylene phase diagram shows the phase behavior with changes in temperature and pressure. The curve between the critical point and the triple point shows the ethylene boiling point with changes in pressure. It also shows the saturation pressure with changes in temperature.

At the critical point there is no change of state when pressure is increased or if heat is added.

The triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.

Back to top

Sponsored Links

Related Topics

Boiling Points

Boiling points of elements, products and chemical species at varying conditions.


Densities of solids, liquids and gases. Definitions and convertion calculators.

Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

Material Properties

Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.

Melting and Freezing Points

Melting and freezing points of elements and chemical species at varying conditions.


Work, heat and energy systems.


Viscosities of products and chemical species at varying conditions.

Related Documents

Air - Thermophysical Properties

Thermal properties of air at different temperatures - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusivity and more.

Critical Temperatures and Pressures for some Common Substances

Critical temperatures and pressures for some common substances like air, alcohol, ether, oxygen and more.

Liquids - Latent Heat of Evaporation

Latent heat of vaporization for fluids like alcohol, ether, nitrogen, water and more.

Speed of Sound Equations

Calculate the speed of sound (the sonic velocity) in gases, fluids or solids.

Water - Thermophysical Properties

Thermal properties of water at different temperatures like density, freezing temperature, boiling temperature, latent heat of melting, latent heat of evaporation, critical temperature and more.

Sponsored Links


Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

This website use cookies. By continuing to browse you are agreeing to our use of cookies! Learn more