Boiling points of Methane (CH4) ,Methanol (CH3OH) and Methyl Chloride (CH3Cl):

What is Boiling point ?

The boiling point of any substance is the temperature at which the vapour pressure of a liquid becomes equal to the atmospheric pressure or external pressure.

Here in the following is Definitions and Boiling points of Methane (CH4) and compounds forming from methane as Methanol (CH3OH) and Methyl Chloride (CH3Cl).

Boiling point of methane (CH4).

Methane is simplest aliphatic hydrocarbon having chemical formula CH4. Methane is also called Marsh gas or we can say it methyl hydrides. Methane is found as second most important gas of greenhouse.It has low melting (M.P) and boiling points (B.P) due to very weak intermolecular forces of attraction.

Methane is lighter than air. It has specific gravity of 0.054. It is slightly soluble in water. It burns readily in air forming CO2 and water vapors.

The boiling points of methane is -162°C (-259.6 °F) and the melting point is −182.5 °C (−296.5 °F).

Factors which effects Boiling Point:

  •  Intermolecular forces which effect the boiling points:

Ionic bonds > Ion dipole Interactions >H-Bonding > Dipole-dipole interactions > Vander Walls dispersion forces.

  • Increasing the numbers of carbon atoms increase the boiling points (BP)
  • Branching with the carbon atoms decrease the boiling points.

3D structure of methane

3d structure of methane

Boiling point of Methanol (CH3OH):

Methanol has different names as methyl alcohol; Carbinol; Methyl hydroxide;  e.t.c… Methanol (CH3OH) has melting and higher boiling point than that of methane and Chloromethane because it has strong intermolecular forces between carbon and oxygen atoms. Below image shown the vapor pressure of methanol:

MethaneVaporPressure

Methanol is simplest alcohol consisting of a methyl group linked to a hydroxyl group. It is polar liquid at room temperature. Boiling point of (CH3OH) decrease with decrease of atmospheric pressure so it will be slightly low when you go to sea level.

It is also known as wood alcohol because it was firstly produced by destructive distillation of wood.

Boiling point as compared to water:

Boiling point of alcohol as compared to water boiling point and other solvents can be determined by doing distillation. In this process when we mixed both compound water and alcohol ; the more volatile compound boil first ; the compound left behind which have high boiling point. As boiling point of water is (212°F) or (100°C) and that of alcohol is -162°C (-259.6 °F) so water has high boiling point than alcohol; alcohol boil and change into vapours first water left behind.

Methyl Chloride:

Methyl chloride is colorless, odorless and flame able gas. It is also called Chloromethane having chemical formula CH3Cl.

When methane reacts with Metal Chloride it forms Methyl Chloride e.g.

CuCl4 + CH4 CH3Cl + CuCl2 + HCl

Methyl Chloride has Melting point -97.4°C(-143.3°F) and boiling point 23.8°C (-108°F) hence melting and boiling points of different compounds vary at different pressure.

Order of intermolecular forces in Methane, Methanol and Methyl Chloride:

Methanol >Methyl Chloride > Methane

Order of boiling points of Methane, Methanol and Methyl Chloride:

Methanol > Methyl Chloride > Methane

Table Below showing Properties of Methane (CH4), Methyl Chloride(CH3CL) and Methanol (CH3OH).
Methane(CH4)Methyl Chloride

(CH3CL)

Methanol

(CH3OH)

Intermolecular

forces

weakStrongVery strong
Melting points−182.5°C −296.5°F  -97.4°C   -143.3°F -97°C     -143°F
Boiling points at room Temp.-162°C -259.6°F23.8°C (-108°F)65°C(-259.6°F
Molar Mass16.042g/mol50.49g/mol32.04g/mol
Vapor pressure62.12MPa506.9 kPa13.02KPa
Density0.657g/L1.003g/mL0.792g/cm3