Ethene is an organic molecule composed of two carbon atoms, joined by a double bond, and four hydrogen atoms.

Ethene, like all molecules, exhibits London dispersion forces. This molecule, however, has no net dipole moment, so it will not exhibit dipole-dipole attraction. Also, even though it contains hydrogens, it does not exhibit hydrogen bonding. To exhibit hydrogen bonding, the hydrogen atoms must be attached to more electronegative atoms, namely nitrogen, fluorine, or oxygen. Finally, ionic bonding is only present in ionic compounds, not organic compounds.

Ionic bonds are the strongest type of bonds, followed by covalent bonds, hydrogen bonds, and lastly, van Der waals forces.

Although the two molecules seem similar in structure, proponol has a higher boiling point due to the hydrogen bonding allowed by its alcohol group. This creates a strong intermolecular force, and extra energy is subsequently needed to break these bonds, resulting in a higher boiling point.

System pressure and temperature are related to boiling point, but are not necessary when comparing the properties of two molecules.

Ionic and covalent bonds are not intermolecular forces;

Ion-dipole>hydrogen bonds>dipole-dipole>van Der Waals forces

This is butanol. It is an alcohol; OH is the prime example of hydrogen bonding, which is the strongest intermolecular force.

Ion-dipole forces are the strongest of the intermolecular forces.

Hydrogen bonding is a specific term for a particularly strong dipole-dipole interaction between a hydrogen atom and a very electronegative atom (oxygen, fluorine, or nitrogen). However, hydrogen bonds are still not as strong as ion-dipole interactions.

In order from strongest to weakest, the intermolecular forces given in the answer choices are: ion-dipole, hydrogen bonding, dipole-dipole, and Van der Waals forces.

Ionic bonding is stronger than any of the given intermolecular forces, but is itself NOT an intermolecular force. Ionic bonds are a permanent chemical connection between two atoms, whereas intermolecular forces as a more transient and temporary attraction between independent molecules.

Formaldehyde, like all atoms and molecules, will have very weak London dispersion forces created as electrons shift within the electron cloud. Because it possesses a permanent dipole (based on the polarized carbon-oxygen bond), formaldehyde also exhibits dipole-dipole interactions. It does not, however, exhibit hydrogen bonding, because no hydrogens are attached to oxygen (or other electronegative atoms like nitrogen or fluorine).

There is a key difference between atomic bonds and intermolecular forces. Metallic bonds, ionic bonds, and covalent bonds are all atomic bonds. This means that they are generally stable and relatively irreversible. An atomic bond will change the identity of a compound by adding an atom to the structure.

Intermolecular forces, in contrast, are more transient and less stable. These attractions are constantly broken and reformed as molecules move around. Hydrogen bonds, dipole-dipole interactions, and van der Waals forces (London dispersion forces) are some common examples of intermolecular forces. Intermolecular forces will never change the identity of the molecule and cannot be used to add atoms to a compound.

There is a key difference between atomic bonds and intermolecular forces. Ionic bonds and covalent bonds are atomic bonds, meaning they are intramolecular. This means that they are generally stable and relatively irreversible. An atomic bond will change the identity of a compound by adding an atom to the structure.

Intermolecular forces, in contrast, are more transient and less stable. These attractions are constantly broken and reformed as molecules move around. Hydrogen bonds, dipole-dipole interactions, and van der Waals forces (London dispersion forces) are some common examples of intermolecular forces. Intermolecular forces will never change the identity of the molecule and cannot be used to add atoms to a compound.

The strongest intermolecular force is hydrogen bonding, which is a particular subset of dipole-dipole interactions that occur when a hydrogen is in close proximity (bound to) a highly electronegative element (namely oxygen, nitrogen, or fluorine). The hydrogen takes on a partial positive charge and the electronegative atoms takes on a partial negative charge.

This is a question about intermolecular forces, or IMFs. There are four broad categories of IMFs, all of which are represented here. 

Since the question asks us to order the compounds from least strength to greatest, we'll start with the weakest IMF: Van der Waals forces, also called "induced dipoles" or London dispersion forces.

Non-polar molecules like  and  can still exhibit temporary dipoles by induction, when the electrons of one molecule push away the electrons of another. In general, the more electrons that are available to push, the more potential there is for a dipole to occur. Therefore,  is weaker, because it has less electrons available than . 

The next tier of IMF is permanent dipole interactions (dipole-dipole interactions) that are not hydrogen bonds.  is a polar molecule and experiences dipole interactions, which makes it the next strongest in our list.

Next is hydrogen bonding, an especially powerful form of dipole interactions when hydrogen is bonded to a fluorine, oxygen, or nitrogen atom.  experiences hydrogen bonding because it has hydrogen atoms bonded to oxygen atoms. Because hydrogen bonds are a stronger form of dipole interactions, this puts  next in the list.

The strongest form of intermolecular force is ionic forces, which exist in ionic compounds like . So,  exhibits the strongest IMFs.

Our final order is , or II < III < IV < I < V.