Final answer:
To determine the highest boiling and melting points of substances, molecular weight, intermolecular forces, and molecular shape should be considered. Substances with similar molecular weights can have different boiling points due to varying forces. Option C is the correct choice.
Step-by-step explanation:
To determine what substances have the highest boiling and melting points, we need to consider multiple factors. One approach is to look at the following three characteristics: molecular weight, intermolecular forces, and shape. Compounds with higher molecular weight generally have higher boiling and melting points. Also, the strength of intermolecular forces, such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding, significantly impacts these temperatures. Lastly, the shape of a molecule can affect how tightly the molecules pack in the solid form, influencing the melting point.
It's important to note that substances with similar molecular weights can have very different boiling points due to differences in polarity and types of intermolecular forces. For instance, nonpolar molecules with large dispersion forces can have higher boiling points than lighter polar molecules with dipole-dipole interactions. In summary, option C) Intermolecular forces, molecular weight, and shape is the correct answer.