CHEM 1A03 LECTURE #2
September 12 2012
**iClicker for marks starts Tuesday the 18 . Oxidation numbers: ref p.85 fig 3.2
Empirical Formula: Reduces to the most common denominator of molecule. For
instance, empirical formula for benzene is CH, while molecular
formula is C6H 6
Molecular Formula: Actual numbers of each element are represented.
Condensed Formula: Empirical formula in brackets, with common denominator on the
outside. For instance, the condensed formula for benzene is
Isotopes: Elements which share the same # of protons, but differ in # of neutrons and
therefore differ in mass #.
A = Mass Number (neutrons +protons) Z = Atomic # (number of protons)
Z identifies which element it is, A identifies the isotope.
Isotopes have natural abundance, which means they are found in statistically uniform
distributions around the world. Finding changes/trends in these distributions allow
scientists to analyze changes in nature, i.e. Calibrating rainfall vs. snowfall per era in
Measuring O/ O ratios in ice cores lets us ‘measure’ past world T (with data
calibrated against the recent past) – evidence for global warming.
September 13/14 2012 2
It’s a “climate proxy” (preserved physical characteristic of the past)
Kelvin is measured on the absolute temperature scale: 0K = Absolute Zero
Celsius is a more traditional style, 0 C = 273K.
These figures change in a 1:1 ratio. Therefore, changes in temperature have the same
value, regardless of T scale.
Extensive vs. Intensive Quantities
Extensive properties: depend on the amount of substance involved i.e. m,V, heat (q)
Intensive properties: independent of the