Final answer:
The more surface-to-surface contact between particles of a substance, the larger the boiling and melting points due to stronger intermolecular forces that require more energy to overcome. Larger molecules typically have greater surface area, leading to increased interactions such as London dispersion forces, which contribute to this effect.
Step-by-step explanation:
The relationship between surface-to-surface contact and boiling and melting points is a key concept in understanding intermolecular forces and their impact on substances. When comparing substances under the same conditions, the one with more surface-to-surface contact between its particles generally has larger boiling and melting points. This is because an increase in surface area allows for more extensive interactions between molecules, such as increased London dispersion forces, which subsequently requires more energy to overcome in the processes of melting and boiling. These principles are observed in the behavior of different compounds and their physical states at various temperatures.
As an example, larger molecules with greater molar masses tend to display higher boiling points due to this increased surface area. However, it is important to note that the nature of the intermolecular forces—whether they are London dispersion forces, hydrogen bonds, or ionic bonds—also plays a significant role in determining these thermal properties. Moreover, the phrase 'The more surface-to-surface contact, the... boiling and melting points.' is completed as 'larger' in response to the question asked, indicating that increased surface area correlates with higher boiling and melting points.