Density and Excel

We started off class by being told by Mr. Lieberman that we will be going to the math lab very quickly so he can show us how to make our graphs for post lab question one for the density of pennies lab. You are supposed to go on microsoft excel and then fill in the the A column with the calculated volume of the pennies. We just did the pre 1982 pennies for now. Then in the B column you type in the mass of the pennies. After we put in the numbers we made a graph of the numbers and printed it out and we have to staple it or glue it in our lab books. To make the graphs we first highlighted the data. Then you click on the insert tab and click charts and choose a type of graph. Next to make the x axis say volume you click on the chart itself then click the layout tab and choose labels. Then click axis titles and it will say x axis and y axis and click on those to be able to make a label for the axis. We left the math lab and came back to the classroom and started talking about density.

Mr. Lieberman showed us an experiment about density and in the experiment he set two beakers up with clear liquids in each and they had approximately the same volume, but Mr. Lieberman never said they were both the same liquid. Next he dropped an ice cube in each beaker and immediately one ice cube sunk and the other floated. The reason why it sunk was because the ice cube had a greater density than the liquid. The other ice cube floated because it had a smaller density than the liquid.

Here are some things you should know about density: it measures how much mass there is a an amount of space which is volume. The way to calculate density is mass divided by volume. Also be sure you know how to calculate volume if you were given mass and density and how to calculate mass if you were given volume and density. There is a special triangle to help those of you who are 'algebraically challenged' that will help you remember these formulas. Just another regular day in sixth period chem.

And the next scribe is....Becky N.

How Dense are your Pennies?

Today we began class by going over quiz 1.2 (measurements and sig figs) which we took yesterday. Mr. Lieberman is a grading machine and was able to grade them in one night! (even with parent night which was described as "wild")

We then began the Density of Pennies Lab. Together we did the Pre-Lab questions. The first question dealt with the estimated uncertainty in a 100 mL graduated cylinder. We found the answer to be one-tenth of a mL. The second question was about calculating the average volume of a metal cylinder. To do this, we subtracted the initial volume from the final volume. We answered this question together in our groups.

Before beginning the lab, we all put on our fashionable safety goggles, because, well, when dealing with pennies...you just never know! The purpose of the lab was to plot mass and volume data for a set of pennies, both pre and post 1982. The data would then be analyzed to identify the identity of the metal that makes up the penny.

We started out by counting out 25 pre-1982 pennies. Then we recorded the masses of 5, 10, 15, 20, and 25 pennies. We filled a graduated cylinder with water to a start value around 50.0 mL. We gently dropped five pennies into the graduated cylinder and recorded the new volume of the water. We continued this process with the rest of the pennies by adding five at a time after recording each volume. To calculate the volume of the pennies, we subtracted the start value from the new volumes. We repeated these steps with the 25 post-1982 pennies. There are Post-Lab questions which are due with the rest of the lab on Monday. Mr. Lieberman said not to worry about the graph because we are doing that in class tomorrow!

And...drum roll please...the scribe for tomorrow is Deena M.!

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.