Chem 109 - General Chemistry - Spring 2013
Lecture Notes 2: 25 January
Note Amy Cuddy video link and study suggestions on notes for first day.
What is Chemistry?
Chemistry is the study of matter and its transformations.
- "Classical" chemistry involves mostly electron transfers and/or interactions of charges (electron and nuclear). As we'll see only some electrons in atoms are involved - the outer or valence electrons of atoms.
- Nuclear chemistry is an extension of chemistry where nuclei are transformed changing one kind of atom (element or isotope) to another. This is a completely separate realm of phenomena, largely unimportant in everyday life (unless you work at a nuclear power plant!).
More specifically, chemistry is the scientific study of matter. So what do we mean by science? Two common "definitions" for Science:
- The body of knowledge and rules/laws/theories we have discovered regarding the natural world.
- The method of discovery and confirmation used by scientists. Classically we describe this process as the "Scientific Method" summarized in the steps below:
- Identify a problem based on initial observations
- Make a hypothesis (a tentative, testable, explanation of the observations)
- Collect data via planned Observations and/or Experiments ("asking nature a question")
- "Clean" simple experiments vs. statistical inference
- Controls - everything the same except the variable of interest.
The remaining steps are noted below:
- Analyze and Evaluate results - modify hypothesis if necessary, and repeat data collections etc.
- Create a theory (an explanation of observations consistant with results of experiments etc.)
- The theory is a "model of reality"
- Note we also use models which are not intended to represent reality, but rather are used to solve particular problems within a defined "universe" which may mimic the behavior of a restricted subset of "reality."
For measurements we want to be sure we convey the precision (repeatability) of our measurements using significant figures. [covered in lab & problem set] You should note a couple of aspects of significant figures:
- They are only used for measured quantities, and
- You will be graded on them all semester, so learn them early and well, or you could lose a significant number of points!
What is the reading (clicker question for last digit)? (0.18±0.01)
What is the measured value (clicker question for last digit)? (1.72±0.01)
© R A Paselk
Last modified 25 January 2013