Chemical Bonds
Topic outline
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Written by: Suzanne Monir, EIS Education Team Member, December 2015
Title of Lesson: Chemical Bonds
Topic: Intermolecular and Intramolecular bonds, Surface tension, Capillary action
Grade (Age) Level: High School (Ages 14-18), UniversityThis course module is a summary of various intramolecular and intermolecular bonds that exist in chemistry with applications to surface tension and capillary action. The impact of bonding should be considered in its own right or as an integral aspect of the majority of microgravity experiments.
Course Index:
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Forum
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Recall that that there are three basic states of matter: solid, liquid, and gas.
In general, compounds with similar bonds have different physical properties depending on their mass. The heavier a compound is, the more London dispersion forces it has and thus it will be more like a solid. We compare how a solid will be a solid, liquid or gas by comparing their melting points (mp) or boiling points (bp). Melting point is the temperature that a substance is converted from a solid to a liquid, and the boiling point is the temperature that substance is converted from a liquid to a gas.
Have a look at this short animation to help you understand the difference.
The lighter a substance is, the lower the boiling point. For example, the boiling point of CH4 is much lower than SiH4 as the elements in the family get progressively heavier, they keep increasing.
BUT, look at the graph below.
Some substances
clearly are not following this trend. In
particular, look at H2O compared to H2S. H2O clearly has a smaller mass
than H2S but H2O has the higher boiling point! Water is clearly an exception to the trends
we just discussed for London Dispersion.
And the reason is… there is much more going on than just London
Dispersion! What is the more predominate
intermolecular bond in H2O?
Well, we have hydrogen directly attached to oxygen so that can only be…
hydrogen bonds! Water is known as the
universal substance and is an important part of all biological beings. Water has a higher boiling point because of
its intermolecular forces! Similarly, NH3 and HF, which also hydrogen bond, are anomalies in the trends of analogous compounds in their groups.