Methane (CH₄): Thermophysical Properties and Phase Diagram

Comprehensive thermophysical properties calculator for methane (CH₄), including critical point parameters, density, viscosity, thermal conductivity, heat capacity, and phase diagram information. Methane is a colorless, odorless gas used as feedstock for chemical industry and as the main constituent of natural gas.

Property	Value	Unit
Autoignition Temperature	810 / 537 / 999	K / °C / °F
Boiling Point	111.51 / -161.6 / -259.0	K / °C / °F
Critical Density	10.139 / 162.7 / 0.3156 / 10.15	mol/dm³ / kg/m³ / slug/ft³ / lb/ft³
Critical Pressure	4.5992 / 45.99 / 45.39 / 667.1	MPa / bar / atm / psi
Critical Temperature	190.56 / -82.59 / -116.66	K / °C / °F
Critical Volume	98.63 / 0.00615 / 3.169 / 0.0985	cm³/mol / m³/kg / ft³/slug / ft³/lb
Density (gas at 25°C, 1 atm)	41.0 / 0.657 / 0.00127 / 0.0410	mol/m³ / kg/m³ / slug/ft³ / lb/ft³
Density (gas at STP)	44.7 / 0.7168 / 0.00139 / 0.0447	mol/m³ / kg/m³ / slug/ft³ / lb/ft³
Density (liquid at -162°C)	26429 / 422.6 / 0.820 / 26.38	mol/m³ / kg/m³ / slug/ft³ / lb/ft³
Flammable	Yes
Flash Point	85 / -188 / -306	K / °C / °F
Gas Constant (R)	518.28 / 0.1440 / 3099 / 96.329	J/(kg·K) / Wh/(kg·K) / ft·lbf/(slug·°R) / ft·lbf/(lb·°R)
Gibbs Free Energy of Formation	-51 / -3179 / -1367	kJ/mol / kJ/kg / Btu/lb
Heat of Vaporization	8.19 / 511 / 219.48	kJ/mol / kJ/kg / Btu/lb
Specific Heat (Cp)	35.8 / 2.232 / 0.533	J/(mol·K) / kJ/(kg·K) / Btu/(lb·°F)
Specific Heat (Cv)	27.4 / 1.709 / 0.408	J/(mol·K) / kJ/(kg·K) / Btu/(lb·°F)
Heat of Combustion	-890.8 / -55528 / -23.9	kJ/mol / kJ/kg / Btu/lb
Heat of Formation	-75.00 / -4675 / -2010	kJ/mol / kJ/kg / Btu/lb
log KOW	1.09
Melting Point	90.55 / -182.6 / -296.7	K / °C / °F
Molecular Weight	16.042 / 0.03537	g/mol / lb/mol
Solubility in Water	0.022	mg/ml
Sound Velocity	446	m/s
Specific Gravity (relative to air)	0.554
Specific Heat Ratio (Cp/Cv)	1.31
Specific Volume	0.0244 / 1.52 / 784.44 / 24.38	m³/mol / m³/kg / ft³/slug / ft³/lb
Standard Molar Entropy (S°)	186 / 11.59 / 2.77	J/(mol·K) / kJ/(kg·K) / Btu/(lb·°F)
Surface Tension (at -161°C)	14 / 0.014	dynes/cm / N/m
Thermal Conductivity	0.0339 / 0.019587	W/(m·°C) / Btu/(hr·ft·°F)
Triple Point Pressure	0.011696 / 0.117 / 0.115 / 1.70	MPa / bar / atm / psi
Triple Point Temperature	90.69 / -182.456 / -296.42	K / °C / °F
Vapor Pressure (saturation)	62.12 / 466000 / 613.07 / 9010	MPa / mm Hg / atm / psi
Vapor Pressure (at 38°C)	34.47 / 258574 / 340.18 / 4999	MPa / mm Hg / atm / psi
Viscosity (dynamic)	0.01107 / 7.44 / 0.23	cP / (lbm/(ft·s)×10⁻⁶) / (lbf·s/ft²)×10⁻⁶
Viscosity (kinematic)	17.08 / 183.8	cSt / (ft²/s)×10⁻⁶

Methane Phase Diagram

Methane exhibits different phases (solid, liquid, gas) depending on temperature and pressure conditions:

Critical Point: At 190.56 K (-82.59°C) and 4.5992 MPa, there is no distinction between liquid and gas phases.
Triple Point: At 90.69 K (-182.456°C) and 0.011696 MPa, solid, liquid, and gas phases coexist in thermodynamic equilibrium.
Boiling Point: At normal pressure (1 atm), methane boils at 111.51 K (-161.6°C).

Key Properties at Standard Conditions (25°C, 1 atm)

State: Colorless, odorless gas
Density: 0.657 kg/m³
Molecular Weight: 16.042 g/mol
Specific Gravity: 0.554 (relative to air)
Flammable: Yes (Autoignition temp: 810 K / 537°C)
Thermal Conductivity: 0.0339 W/(m·°C)
Specific Heat (Cp): 2.232 kJ/(kg·K)

Applications

Methane is primarily used as:

Feedstock for chemical industry
Main constituent of natural gas
Energy source for heating and power generation