More figs, more fun! Sig Figs..

Well, maybe it's not exactly fun, but today class was all about the numbers in chemistry. More specifically, Sig Figs, or Significant Figures.

To start things off, we first went over the Metrics worksheet we had for homework. (Some new metric measurements that were not in the notes was hectogram (hg) which is equal to 100 grams, and cm^3 = 1 ml) One of the things we checked checked for was estimating past the last readable digit, meaning if the last digit of a measurements is in tens, then you would estimate to ones to leave room for error.

On a bit of a side note, the last problem on the worksheet showed an illustration of a buret, which appears to be measuring upside-down, but is in fact correctly labeled. Mr. Lieberman told the class that we would be using this instrument a lot in second semester. (I added the picture simply because of the lack of color....and for a visual of course..)

For the rest of class, we got another worksheet (for homework) and went over notes for sig figs and scientific notation, which is, as most of us already know, something like 590000 to 5.9 x 10^5 to show the number of significant numbers.
However there are also some rules to sig figs that play into measurements and the scientific notation. For precision's sake, these rules are:
-nonzero integers count as sigfigs
-leading zeros are never significant (0.000757 has 3 sig figs)
-captive zeros always count as significant figures (such as in 16.07, there are 4 sig figs)
-trailing zeros are only significant if the number contains a decimal point (9.300 has 4 sig figs. If the number were 500, there is only one sig fig, unless it was written as 500.0.)

For mathematical operations, there are different rules for adding/subtracting and multiplying/dividing:
Adding/subtracting : the # of sig figs in the result equals the number of decimal places in the least precise measurement.
EX: 6.8 + 11.938 = 18.734, which turns into 18.7 (for 3 sig figs)

Multiplying/dividing : the # of sig figs in the result equals the number in the least precise measurement used in the calculation.
EX: 6.38 x 2.0 = 12.76, which becomes 13 (2 sig figs)

(All of these notes can be found on the powerpoint)

And with a schedule that was shifted around, we ended class in 40.0 minutes.
As a reminder, we have a quiz on the measurements and sig figs we went over tomorrow. The quiz Mr. Lieberman assured would not be as easy as our first quiz.. Good luck to us all..
and the chosen one to be scribe tomorrow will be... Zoe S.