I am a specialist in the field of physical chemistry, and I'm here to provide a detailed explanation on why methane has a very low boiling point.

Methane, with the chemical formula CH4, is the simplest alkane and the primary component of natural gas. Understanding the boiling point of methane requires an exploration into the forces that hold molecules together in the liquid phase and the energy required to overcome these forces to transition into the gaseous phase.

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure, typically atmospheric pressure. For a substance to boil, the kinetic energy of its molecules must be sufficient to overcome the intermolecular forces that keep them in the liquid state.

**Methane's low boiling point is primarily due to the type of intermolecular forces present between its molecules.** Methane is a non-polar molecule because it has a symmetrical tetrahedral shape and the centers of positive and negative charge coincide, resulting in no net dipole moment. This lack of polarity means that there are no strong dipole-dipole interactions or hydrogen bonds between methane molecules, which are the types of forces that would require more energy to break.

Instead, methane molecules are held together by London Dispersion Forces, also known as van der Waals forces or induced-dipole induced-dipole interactions. These forces arise from temporary fluctuations in electron distribution that create temporary dipoles, which then induce dipoles in neighboring molecules. The strength of London Dispersion Forces is dependent on the size and shape of the molecules; larger molecules with more electrons have stronger London Dispersion Forces.

However, for methane, these forces are relatively weak compared to the forces in more complex molecules. The reason for this is twofold:


1. Methane's Small Size: Methane is a very small molecule with only one carbon atom and four hydrogen atoms. Its molecular weight is low, which means there are fewer electrons to generate the temporary dipoles necessary for London Dispersion Forces.


2. Lack of Polarity: As mentioned, methane's non-polar nature means that the electrons are evenly distributed, and there are no strong permanent dipoles to induce significant temporary dipoles in neighboring molecules.

The boiling process involves the molecules gaining enough energy to overcome these weak London Dispersion Forces. Since these forces are easy to break, the energy required is relatively low, which is why methane boils at a low temperature of approximately -161.5°C (-258.7°F) under standard atmospheric pressure.

It's also worth noting that the boiling point of a substance can be influenced by other factors such as molecular weight, molecular shape, and the presence of functional groups that can form hydrogen bonds or other stronger intermolecular forces. However, in the case of methane, these factors are not significant due to its simple structure and non-polar nature.

In summary, the low boiling point of methane is a direct result of the weak intermolecular forces present between its molecules, specifically the London Dispersion Forces, which are easily overcome at low temperatures due to methane's small size and non-polar nature.

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Because methane (CH4) is a non-polar molecule the molecules are held together only by London Dispersion Forces which are very weak and easy to break. These bonds break when methane boils and because they are weak, it boils at a low temperature.Nov 2, 2014read more >>