Why water exists as a liquid at STP while methane(CH4)exists as gas even though their molecular mass are close

Question

Explain why water exists as a liquid at STP, while methane (CH4) exists as a gas, even though their molecular masses are fairly close to each other.

Answer 1

Even though water has MM about 18 and methane has MM about 16 and usually state of matter depends on MM, the bonding and geometry of the molecules are what make the difference .

Water has polar covalent bonds and is bent. This means that water forms hydrogen bonds with other water molecules.

CH4 has nonpolar covalent bonds and is tetrahedral, so is nonpolar. The only attraction between methane molecules is Van derWaal's forces, which is less than polar (H) bonds.

Answer 2

Water has a dipole, the oxygen has a slightly negative charge, and the hydrogen atoms have a slightly positive charge. Water molecules stick to other water molecules (similar to how two magnets stick together) in a process called hydrogen bonding. Hydrogen bonding holds liquid water together to a greater degree than methane, even thought both compounds have a similar weight and size.

Methane is very symmetrical in the sense that each of the 4 hydrogen atoms is equally distant from its neighbor. The bond angles are all the same. And it is this symmetry that equalizes the electron forces within the molecule.

Answer 3

alright not sure if this will make sense but the shape of water is bent. also oxygen is highly electronegative so the polarity on the O is more negative than the H's. In methane it forms a plus and the pull throughout the molecule is equal. in water, the hydrogen will be more attracted to the oxygens than the hydrogens to other hydrogens in methane so water is more tightly compacted because there is more pull

Answer 4

Water molecules are bound together by hydrogen bonds, which are about 100 times stronger than the van der Waals forces binding methane molecules together. Thus it takes much more energy to separate water molecules into gaseous form, so it has a much higher boiling point.

Answer 5

Hydrogen bonding. Water undergoes extensive hydrogen bonding, the bonding of electron rich atoms (O) to electron deficient atoms (H), which forms and extensive network. This means that much more energy is required to overcome to the liquid/gas phase interface. Which is why is it a liquid and not a gas.