Final answer:
Boiling points, melting points, and surface tension are determined by intermolecular forces, which cause variations in these properties even among substances with similar molar masses. Liquids boil and solids melt when enough thermal energy overcomes these forces. Surface tension relates to the energy required to expand the surface area of a liquid, influenced by the strength of intermolecular interactions.
Step-by-step explanation:
Physical properties, such as melting points, boiling points, and surface tension are critical bulk characteristics determined by intermolecular forces. Substances with similar molar masses can display vastly different boiling points due to the variation in these forces. When discussing liquids, these properties are a direct result of how the molecules interact. For instance, a liquid boils at a temperature where the molecules possess enough thermal energy to overcome the intermolecular attractions, causing them to form vapour bubbles. Similarly, a solid's melting point is reached when thermal energy is sufficient to break the fixed position of molecules. Substances like water illustrate these principles well, as it is a common reference with familiar melting and boiling points. Surface tension is another property influenced by intermolecular forces, where a greater force corresponds to higher tension. This property affects not only how liquids behave at their surface but also how they interact with other substances, like in capillary action or when affected by surfactants.