CH301H - Principles of Chemistry I: Honors
Fall 2012, Unique 51390


Lecture Summary, 30 August 2012

Today we discussed basic problem solving techniques.  We covered the importance of careful analysis of units and the magnitude of the result.  Whenever you solve a problem, you should look at your final answer and ask yourself qualitiative questions about whether that answer makes any sense.  Do the units make sense?  Should the number be > or < 0?  Should it be > or < 1?  Does the magnitude of the number make sense?  If your number doesn't make good physical sense, then you have made a mistake that you need to go back and find.  Getting into this habit will allow you to solve complex problems and have confidence in your answer, even if you don't know what it is.

Matter and Energy:  Matter is neither created or destroyed, and energy is conserved.  Under conditions of very small mass and very large energy, energy and matter can be converted to one another using Einstein's E=mc2, but this is not something we usually care about in chemistry.  Matter can be rearranged so that it takes on very different physical properties, i.e. combining hydrogen and oxygen gas into water vapor.  Chemistry is the science of figuring out how this conversion takes place.

Planetary Model of the Atom:  We also reviewed Rutherford's gold foil experiment which lead to the planetary model of the atom, with a bulky nucleus surrounded by a stable electron in motion.