The following boiling points correspond to the substances listed. Match the boiling points to the substances by considering the relative strengths of their intermolecular forces. b.p. \(\left({ }^{\circ} \mathrm{C}\right)\) : $$ -162,-88.5,28,36,64.5,78.3,82.5,140,205,290 \text {; substance: } $$ \(\mathrm{CH}_{4}, \mathrm{CH}_{3} \mathrm{CHOHCH}_{3}, \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{OH}\) (has a benzene ring), \(\mathrm{HOCH}_{2} \mathrm{CHOHCH}_{2} \mathrm{OH}, \mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{CH}_{3}, \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\). Hint: The boiling point of \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHCH}{ }_{2} \mathrm{CH}_{3}\) is \(28^{\circ} \mathrm{C}\) and that of \(\mathrm{CH}_{3} \mathrm{OH}\) is \(64.5^{\circ} \mathrm{C}\).

Boiling points of substances are a fundamental concept in chemistry, intricately linked with the nature and strength of intermolecular forces within a compound. At a boiling point, a substance changes from a liquid to a gas, and this phase transition occurs when the vapor pressure of the liquid equals the atmospheric pressure. Understanding this concept is pivotal because it helps us predict how substances will behave under different temperature conditions.

For instance, molecules that exhibit strong intermolecular forces such as hydrogen bonding will typically have higher boiling points, as more energy is required to break these forces for the phase transition to occur. Conversely, molecules with weak intermolecular attractions, such as London dispersion forces in non-polar molecules, will boil at lower temperatures. Through comparing boiling points, chemists infer details about molecular structure and strength of attractions, making this attribute a valuable tool in molecular characterization and determination of substance purity.

Chemists often encounter the term London dispersion forces, which are a type of weak intermolecular attraction. These forces are present in all molecules, whether polar or non-polar, and are particularly significant in non-polar compounds. London forces, also called induced dipole-induced dipole attractions, arise due to the constant motion of electrons in atoms and molecules, which leads to fleeting dipoles.

Even though these forces are the weakest of all intermolecular attractions, they influence properties like melting and boiling points, especially in large, non-polar molecules with more electrons, which can lead to stronger London forces. Molecules with greater surface area also tend to have stronger London dispersion forces, resulting in higher boiling points compared to smaller or more compact molecules with a similar molecular weight.

Hydrogen bonding is a particularly strong type of dipole-dipole interaction, but it only occurs when hydrogen is covalently bonded to electronegative atoms such as nitrogen, oxygen, or fluorine. The large difference in electronegativity between hydrogen and these atoms creates a significant dipole. The small size of hydrogen allows these bonds to be highly directional, leading to stronger intermolecular attractions.

When substances contain hydrogen bonds, they exhibit much higher boiling points than those that do not. For example, the presence of an -OH (hydroxyl) group in a molecule raises the boiling point substantially, as indicated by substances like alcohols. Hydrogen bonds also play essential roles in the biological domain, where they are critical for the structure and function of macromolecules such as DNA and proteins.

Chemical structures provide a visual representation of molecules, detailing the arrangement of atoms and the bonds between them. They are essential in understanding the behavior of compounds, particularly how they interact with each other through intermolecular forces. The structure can tell us whether a molecule is likely to participate in hydrogen bonding or merely exhibit London dispersion forces or dipole-dipole interactions.

Examining chemical structures allows chemists to infer physical properties such as solubility, density, and boiling points of substances. The intricacies of molecular geometry further influence these properties; for instance, linear molecules might have different boiling points compared to branched molecules of similar molecular weight due to varying surface contact and intermolecular interactions. Understanding chemical structures is therefore crucial in predicting how a substance will behave in various environments and in designing new compounds with desired physical and chemical characteristics.