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.

Another exciting day in the sixth period chemistry class

Today at the beginning of class, Mr. Lieberman handed back our labs and quizzes. The latter he claimed was a gift to get our hopes up, soon to be crushed by our next quiz on Wednesday. And frankly, i wouldn't put it past him. However, at least he was honest.

We then had a very pleasant surprise: a shootout between Ben, Brandon, and Kaitlin, aiming at a target on the screen using Mr. Lieberman's handy-dandy uzzi-- which is a gun for those of us who don't know. The competition went smoothly except for a single misfire, which thankfully did not harm anybody. The result was a tie between Brandon and Ben each with one point, and Kaitlin in second with zero.

now a few definitions:

• Accurate: hitting what you are aiming for (the target)
• Precise: being consistent every time; your work is reproducible

Nobody was accurate, because nobody hit the bullseye. However Kaitlin was at least precise, hitting the same spot on the floor every time.

Other than that, today was a typical day in the classroom: lecture notes.

We now (in theory) know the metric system: 1g=10dg=100cg=1,000mg=1,000,000um (micrograms)=1,000,000,000 ng=1,000,000,000,000 pg=.001 kg.

The hierarchy of metric prefixes goes like this:

kilo=1000

(none)=1

deci= 1/10

centi= 1/100

milli = 1/1,000

micro= 1/1,000,000

nano= 1/1,000,000,000

pico= 1/1,000,000,000,000

And there is mega and giga and tera, but if you care about those, you probably know what they mean.

We also learned about temperature: Scientist use celsius, in some cases they use kelvin, we use farenheit. The conversion equation is: t(f)=9/5c+32. The way I remember it is how to get from 100 to 212 using 9/5 and 32: multiple by 9/5 to get 180, add 32 to get 212, maybe that helps.

And last but probably not least, taking measurements: Always estimate one digit past the last readable digit. So that means if you are measuring in millimeters, you want to measure to the point "x". If a box happens to be about 11 mm, plus a tiny bit, you would record 11.1 mm.

If you did not understand this I am embedding the notes for todays lecture here:

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YUS, it worked. If you do not understand, comment.

This is Matt P, and always will be.

Michelle T. you have been privileged with the honor of being our next scribe.