Weekly blog 11/4 thorugh 11/10

This week, we learned about vapor pressures, lattice energies, boiling points, and how intermolecular forces affect each of these. The higher the boiling point of a substance, the lower the vapor pressure. This means that the more intermolecular forces in a substance there are, the lower the vapor pressure in that substance. Lattice energy increases as ion size decreases and charge increases. This is a result of the coulombic relationship in lattice energy. Lattice energy is actually correlated with melting point, because ions in a lattice are harder to break from that lattice as lattice energy goes up. This means that when there is more lattice energy, the melting point rises. Here is a link to some good review on lattice energy.

On friday we applied all of these concepts we have learned in an activity where we had to determine if specific substances were or were not conductive, and also we had to identify unknown elements based on their properties. The conductivity test was fairly simple; we put a probe in each of the substances and it told us whether or not it was conductive. We discussed why some substances were conductive only when in a liquid state, like salt. Salt breaks into ions which can then conduct electricity when in liquid form. As for the identifying unknown elements, it was fun. It was interesting to see how some molecules were more viscous than others and to be able to tell which molecule was which just based on things like solubility, viscosity, and vapor pressure. Even though they all had virtually the same viscosity except glycerin, we could still figure it out. The key was testing the solubility with water.

My understanding of what was going on in class is pretty good, I think that I could still understand better why some things are conductive as a liquid but not as a solid. It seems counterintuitive to me, why something that has less density could be more conductive than something with more density. However, I think I'll be able to figure it out. Hopefully Dr. J will have another chat room open on monday night, because I found that enormously helpful when studying for the test last time.