Why doesn't methane have a vapor pressure?

Answer 1

in brief...

- molecules of methane are bonded by dispersion forces

- dispersion forces are the weakest form of intermolecular bonding, meaning that there is only a small amount of energy (or heat) required to break the weak dispersion forces between the methane molecules

- because there is not much heat required to break dispersion forces - we can understand why methane boils so easily and at such a low temperature

[explanation of dispersion forces in more detail...

- electrons inside an atom move around the nucleus randomly

- it is likely that, at any one instant, there may be more electrons on one side of the nucleus than the other

- this results in one side of the atom being more negatively charged than the other at this instant (the side with more electrons on it than the other would obviously be more negatively charged)

- now to explain how this applies to intermolecular bonding...well - to make things easier, I'll name one molecule BOB and another STEVE. imagine that STEVE is standing to BOB's left. if say, we froze time - and at that instant there were more electrons on the left hand side of BOB's body - the left hand side of BOB would become negatively charged. the electrons inside STEVE (who is standing to BOB's left) would suddenly be repelled to his left, as far away from the negative side of BOB as possible. thus the right hand side of STEVE would become positively charged while the left hand side of STEVE would become negatively charged just like BOB. this would continue on in a domino kind of a way to surrounding molecules - and the attraction between the negatively charged side of BOB and the positively charged side of STEVE is what we call dispersion forces.

in more scientific terms: dispersion forces are the attraction that exists between molecules because of the temporary dipoles (differences in charge of one side of a molecule to the other) that form as electrons move randomly

- dispersion forces are very, very weak - which explains why molecules that are bonded in this form have such low boiling temperatures]

Answer 2

It does! The term vapor pressure only applies to liquids however, and at room temperature and normal pressure, methane is a gas.

However, if you cool it down cold enough to liquify it, methane would have a vapor pressure just like any other liquid.

Answer 3

in brief...

- molecules of methane are bonded by dispersion forces

- dispersion forces are the weakest form of intermolecular bonding, meaning that there is only a small amount of energy (or heat) required to break the weak dispersion forces between the methane molecules

- because there is not much heat required to break dispersion forces - we can understand why methane boils so easily and at such a low temperature

[explanation of dispersion forces in more detail...

- electrons inside an atom move around the nucleus randomly

- it is likely that, at any one instant, there may be more electrons on one side of the nucleus than the other

- this results in one side of the atom being more negatively charged than the other at this instant (the side with more electrons on it than the other would obviously be more negatively charged)

- now to explain how this applies to intermolecular bonding...well - to make things easier, I'll name one molecule BOB and another STEVE. imagine that STEVE is standing to BOB's left. if say, we froze time - and at that instant there were more electrons on the left hand side of BOB's body - the left hand side of BOB would become negatively charged. the electrons inside STEVE (who is standing to BOB's left) would suddenly be repelled to his left, as far away from the negative side of BOB as possible. thus the right hand side of STEVE would become positively charged while the left hand side of STEVE would become negatively charged just like BOB. this would continue on in a domino kind of a way to surrounding molecules - and the attraction between the negatively charged side of BOB and the positively charged side of STEVE is what we call dispersion forces.

in more scientific terms: dispersion forces are the attraction that exists between molecules because of the temporary dipoles (differences in charge of one side of a molecule to the other) that form as electrons move randomly

- dispersion forces are very, very weak - which explains why molecules that are bonded in this form have such low boiling temperatures]

Answer 4

The molecule with a high vapor pressure is the molecule with the weaker intermolecular forces. Water has all three intermolecular forces, london dispersion forces, hydrogen bondings, and dipole-dipole forces. Methane, on the other hand, has only london dispersion forces because it is nonpolar. Moreover, we have to consider molecular weights. The molecule with a larger molecular weight will have more london forces involved in bonding in order to stabilize the molecule, and hence would have stronger intermolecular forces because all the weak forces (london forces) will behave as strong forces. Both molecules have similar molecular weights, so we can't compare which molecular is larger. Hence, we have to consider the molecule with the strongest intermolecular force. Hydrogen bondings are the strongest intermolecular forces, and they are seen in water. Thus, water has stronger intermolecular forces. So, the molecule with weaker intermolecular forces is methane, and thus has a higher vapor pressure.

Answer 5

There is only one form of the molecule CH4. Each Hydrogen bond bonds with a single location on the Carbon atom. There is no way to rearrange the Hydrogen atoms, without separating the molecule into multiple molecules.

Answer 6

Methane is a gas at room temperature and pressure, so it does not have a vapor pressure because it is already in the gaseous state. Vapor pressure typically refers to the pressure exerted by a substance in its liquid state when it is in equilibrium with its vapor phase.

Answer 7

Methane is gas derived from liquid methane.

Answer 8

It doesn't. Helium does.