Boiling point

[504939134]

How does a molecules bond type relate to its boiling point? Which types of bonds will cause higher or lower boiling points?

[Michelle Shin 4B]

Stronger bonds have higher boiling points because it takes more energy to boil. Ionic and Hydrogen bonds have higher boiling points while covalent bonds usually have lower boiling points.

[nehashetty_2G]

Since boiling point is the change from liquid to the solid state it is identified when all the intermolecular bonds are broken. Therefore, the stronger the intermolecular forces (IMF) are the higher the boiling point will be. Hydrogen bonding is one of the stronger intermolecular forces and causes high boiling points (like water). Dipole-dipole and dipole-induce dipole are relatively weak IMF forces.

[Helen Struble 2F]

The bond type doesn't necessarily contribute to boiling point, but the IMFs associated with certain bonds do. For instance, ionic salts like NaCl have strong ion-ion forces which give it its high boiling point because it requires a lot of energy in the form of heat to overcome these forces. F₂ is a non-polar molecule, and thus only has induced dipole-induced dipole forces. This contributes to its low boiling point, because it requires far less energy to overcome the relatively weak IMFs. When thinking about boiling point, it's important to remember that heat is energy. So essentially, boiling point comes down to how much energy is required to overcome the IMFs in any given sample.

[Robert Cross 1A]

The bond type doesn't necessarily contribute to boiling point, but the IMFs associated with certain bonds do. For instance, ionic salts like NaCl have strong ion-ion forces which give it its high boiling point because it requires a lot of energy in the form of heat to overcome these forces. F₂ is a non-polar molecule, and thus only has induced dipole-induced dipole forces. This contributes to its low boiling point, because it requires far less energy to overcome the relatively weak IMFs. When thinking about boiling point, it's important to remember that heat is energy. So essentially, boiling point comes down to how much energy is required to overcome the IMFs in any given sample.

Thank you for the helpful example :)

[Juliet Stephenson 4E]

The number of hydrogen bonds/induced-dipole-induced-dipole interactions also contribute to boiling points (as they also contribute to bond length/strength). I found Lavelle's example of A-T vs G-C bonding in DNA particularly helpful. Since A-T has dipole-dipole interactions at two sites, it has a lower boiling point than G-C bonds, which have dipole-dipole interactions at three sites. As a result of this, sequences with more G-C pairs have an overall higher boiling point than sequences with fewer G-C pairs.