The following information needs to be modified due to more specific explanation of Intermolecular Forces (IMF). |
The links below need to be modified due to more specific explanation of Intermolecular Forces (IMF) as will be discussed now. |
<b>Therefore, all species have LDF (or some times dispersion forces) but most of the time, the other IMF make the LDF force insignificant. This is the reason if you compare two different substance with significantly different number atoms/electrons (usually can be seen in molar mass values, the substance with the higher molar mass has a higher IMF (can often be seen with a high boiling point for example) not matter ) |
Therefore, all species have LDF (or some times dispersion forces) but most of the time, the other IMF make the LDF force insignificant. This is the reason if you compare two different substance with significantly different molar mass / Molecular weights (MW) ( i.e. very large difference in number of atoms/electrons), the substance with the higher molar mass has a higher IMF (can often be seen with a high boiling point for example) not matter what type of IMF the two substances have. Of course, it has to be significantly different. The information below will say that LDF are when two non-polar molecules interact. This is NOT inconsistent with the explanation above. Remember, non-polar molecules due to either bonding type and/or symmetrical geometry, on average, the electrons are evenly distributed throughout the compound. So these substance do not exert Coulombic force ( thereby IMF) in any other way except for Instantaneous dipoles (i.e. London Dispersion Forces). Therefore, LDF for these compounds are the only force being exerted. Please keep the above discussion in mind when go to the links below that contains Youtube video, lecture notes. and graphs/figures on IMF and the Physical properties that they cause. [IMF and Physical Properties] *Link to 1st year Bond polar, Molecular polarity, IMF, [Polarity and Intermolecular Force (IMF)] *Other Physical Properties and IMF link **[Physical Properties or Application of Intermolecular Forces (IMF) - Vapor Pressure and Boiling] **[Physical Properties or Application of Intermolecular Force (IMF) - Solubility and Miscibility] *For AP students, there are more physical properties that are caused by IMF that will be discussed in a different webpage (i.e. Surface tension, capillary action/effect, cohesion, adhesion.) |