Friday, September 17

On Friday the first thing that Mr. Henderson asked the class to do was pull out their Unit 1 Packets and a calculator. He then told the class that we would not be staying here long, we would be going to the computer lab to do some graphing and plotting on a program called Graphical Analysis. Mr. Henderson then took attendance and we started to admire Lindsays very well set up blog post of the day before. Mr. Henderson notices that there is a link to a page with some practice for significant digits. He tells the class that for later blogs if we decided to add a link to our blog we could use that same link for our Delicious assignments.

After we had finished admiring Lindsays

blog it was time to get down to business and take a look at page 13 in our unit packets which had some density practice for us. On the page we

needed to know the formula for density which is, Density = Mass/Volume. It also talks about how the units of density are usually expressed in grams/ml or grams/ cubed centimeters. We then do problems 4 and 5. In problem 4 the density is given as 8.933 g/ cubed cm and the mass is 2.62 g. we have to find the volume of the substance so we use the equation for density and plug in the numbers we know, 8.933 = 2.62/x, in order to solve this problem we will have to use algebra. Start be multiplying both sides by 1/2.62 then we get the answer .293295, this is not the answer because we have not put significant digits into consideration yet. since we

divided we use the same amount of digits of the number with the smallest amount of significant digits which would be 2.62 which has 3. So our final answer for this problem would be .293 cubed cm.

We then go to page 14 of our packets and it is similar to what we do in the computer lab. In the computer lab we plot the volume and mass that is given on page 15 and a graph is made. Then because we have to plot our data from the Dense Cents lab, we plot our information from the Pre 82 and 82 coins and the Post 82 coins.

For homework we had to do 2 webassign assignments, finish labs 5, 6,and 7, because we would be getting them checked on tuesday, and finally we have a unit 1 test on thursday.

Thursday, September 16

We started off today’s class by going over last nights blog, done by Alex P. Mr. H then continued on to talk about the expectations for Lab MM5, which was to make sure you wrote a couple of paragraphs describing the chemical reactions of the substances you tested. Mr. H took a few minutes to review the five pieces of evidence that characterize chemical change, which were evolution of gas, solid being formed, production of heat or light, change in color, and temperature change. Next Mr. H started our lesson on density. We went over the Chapter 1.3 reading sheet (page 21) and took some notes on density in the margin.

NOTES FROM CLASS DISCUSSION:

The big idea was that every substance has a unique set of identifying properties; these properties distinguish the substance from other substances. For example: Water is a colorless substance that boils at 100 degrees C, freezes at 0 degrees C, has a density of 1.0 g/mL and a heat capacity of 4.18 J/gC.

· Intensive vs. Extensive Properties

o Intensive- identifying does not depend on amount

o Extensive- (usually volume and mass) depends on amount

· Chemical Properties: describes how a substance reacts (or not) with other substances

· Physical Properties: describes a substance apart from how it reacts

· Three common physical properties: density, solubility, and color

· DENSITY

o A measure of how tightly that mass is packed into a given volume of space

o Density= mass/volume

o Units: g/cm^3, g/mL, kg/L, kg/mL

After Mr. H explained density, he went through the answers to the 1.3 reading sheet:

1. .A

2. .A. PP, B. CP, C. PP, D. CP

3. .FALSE- The density of a material is specific to that material and not dependent on the amount.

4. .A

5. .D

6. B

7. .C

8. .A

Mr. H noticed that many people didn’t understand how to do number 4, which involves knowledge of significant digits. If you still don’t understand or would like to practice it more then you should go to this website or see packet page 6: http://www.physics.uoguelph.ca/tutorials/sig_fig/SIG_dig.htm

After we did our review and notes, Mr. H explained Lab MM7. The lab was called Dense Cents Lab and the question was “What is the density value of pre- and post-1982 pennies? How do their density values compare? How can the difference be explained?” The purpose was to use a plot of mass vs. volume to determine and compare the density value of pre- and post-1982 pennies and to explain the difference between their densities. First each group separated the pennies into two groups, one with pre-82 and one with post-82 pennies.

Then we measured out 50 mL of water into a graduated cylinder. This was going to be used to find the volume of the pennies, using displacement. Displacement is where you add the objects to the water and difference between the original volume and the new volume is the volume of the object. We massed the pennies in groups of 5 up to 30. After massing each group of 5 we then put them in the graduated cylinder to find the volume. We then divided the volume from the mass of each set to find the density.

Based on the data that we collected, the pre-82 pennies seem to have a higher density. The pre-82 pennies had a total density of 50.095 and the post-82 pennies had a density of 53.545.

Wednesday, September 15

We began today's class by briefly looking at the blog. First, we looked at Konstantine's delayed blog from last Friday (due to technical difficulties, of course) and Katie's blog from last night. Mr. Henderson then proceeded to give us a brief lesson on how to use DropShots with the blog. This link provides the portal to the "Chemistry Classroom" account with the access password being "gbs":
http://www.dropshots.com/chemistryclassroom

While showing the class Katie's blog, Mr. M noticed that Katie had embedded an link with excellent practice into her blog. This reminded him of telling us about the Delicious assignment that we have due on Friday, September 17. He said that Katie's link was a perfect example of what we could use for our assignment. He showed us how to log into the database and how to tag and fill out the form for our links. In order to log into this website, we need a Yahoo account. Mr. H told us that it would be useful to have a Yahoo, Google, or Facebook account because those major corporations would end up taking over many of the smaller companies. Thank you for those wonderful words of wisdom, Mr. H! More thorough directions for Delicious can be found on the hand out we received in class on Monday or on the GBS Chem-Phys website:
http://gbschemphys.com/honchem/index.html

After our tech tutorial, Mr. Henderson asked us to take out our unit packets and turn to page 9. Before beginning the worksheet, he quickly reminded us of the differences between a physical (describing the substance without describing its interaction with other substances) and chemical (describing the substance by how it interacts with other substances) properties. To give us a better idea, he told us he would show us an example of a chemical property of magnesium. He showed us the sample of magnesium - a shiny metal - and turned on the methane flow. He lit the burner (from the bottom up, of course) and began to burn the magnesium. Mr. H told us that magnesium reacted very strongly with oxygen to make magnesium oxide and that we should be prepared to see a very bright light, indicating the reaction. Sure enough, when the magnesium heated up enough, we saw a very bright light. Our experience was similar to this video from Youtube:
http://www.youtube.com/watch?v=Q_LU1EASadU

Mr. H then pulled up an overhead of 4 out of the 5 pieces of evidence of a chemical change. They are: bubbling & production of gas, formation of a solid, heat or light, color changes, or temperature changes. The difference between a heat/light change and a temperature change is that the temperature change is more drastic and long term.

As soon as all the explanation was finished, we began page 9 and the "Verbal Description of Change" section. We attempted to do the section individually and went over the activity together and the answers are as followed: C, P, C, C, C, P, P, C. We had to be on the lookout for the chemical changes we learned about in each of the scenarios order to determine the type of change.

Next, we determined the "Symbolic Description of Change" as a class. If the element remained the same, it was a physical change. If the before and after differed from each other, it was a chemical change. The answers are as followed: P, C, C, P.

To finish the page, we flipped it over and determined the "Visual Depiction of Change at Microscopic Level". We had to be on the lookout for changes in the shape and arrangement of the atoms and molecules. The answers are as followed: C, P, C, P.

Abruptly, Mr. H got up and directed us to the back of the room and under the fume hood. He asked us for two pennies. He took our a large bottle of nitric acid and explained to us what a hazardous chemical it was and how we had to be careful when handling it. Mr. H was going to demo the reaction between copper and this nitric acid. He poured the acid into a flask and diluted it with some water. He dropped one of the pennies in and told us to observe. Meanwhile, he took another flask and filled it with pure nitric acid. He dropped the copper penny into the substance and told us to observe and compare it to the other flask. Immediately, we saw a change of color. The acid went from clear to a gradient green-red. Bright orange gas began spewing out of the top of the beaker. It bubbled and displayed a clear chemical change. The diluted beaker was showing the same changes (minus the color change and significantly less bubbling and gas) at a much slower rate. Mr. H ask Katie to touch the beakers carefully. She told the class they were both very warm, indicating a temperature change. It was very interesting to see the copper penny dissolving and reacting with the acid. The flask with the pure nitric acid and penny looked similar to this photo:

We concluded the class by returning to our seats. Mr. Henderson quickly read us a story about a man whose experience with nitric acid inspired him to keep experimenting with it. With little time left, we were instructed to turn to page 11 and complete the "Verbal Description of Change" and determine the Physical and Chemical properties. The answers are as followed: P, C, C, P, C, P, C, C, P.

Just as the bell was about to ring, Mr. H handed out the quizzes from last week and told us to check our answers and use it as a guide. He told us that tomorrow we could expect a lab about density and that our homework was finishing the 1.2 Webassign and our Delicious assignment.

Friday September 10, 2010

Today's class started off by getting our lab notebooks back. Mr. H graded Labs 1-4, but didn't tell us our grades in our lab notebooks. He told us that he wrote comments and suggestions in most lab books.

Mr. H then had everyone take out their chemistry packets and he went over the question on the bottom of page 6, which was about listing significant numbers when adding, subracting, multiplying, and dividing. He went over significant numbers again and how many to include when adding, subtracting, multiplying, and dividing. The rules are as followed when adding/subrtracting or multiplying/dividing:

Addition/Subraction: The number of decimal places in the result is equal to the number of decimal places in the quantity with the least certainty (i.e., least number of decimal places).

Multiplication/Division: The number of significant figures in the result is the same as that of the quantity with the least number of significant figures.

Mr. H then worked with the class on the first two practice problems to clarify what the rules were saying. He then had us work on the rest of the practice problems by ourselves. After a few minutes of working Mr. H revealed the answers to the class, so everyone was able to check their answers. He answered a few questions from students and then he went to our class's chem blog.

Mr. H went over Hannah's and Neil's blog posts and then gave a few tips on how to make both blogs a bit better for next time.

Mr. H then had the class open up their chemistry packets to the last page to look over today's lab, which was MM6 Conservation of Mass Lab. As the class wrote down the purpose, he explained what we were going to do in today's lab and what to expect. He told the class that since we were going to be dealing with liquids and chemical reactions, that we should wear our safety glasses. He explained to us that we were to find the mass of a flask before the chemical reaction and after, and then compare the differences.

As everone went to their lab stations, they first began by pouring a blue liquid into a flask and then put a testing tube filled with a white substance. Groups then went and measured the flask with all its components as shown below. 

Click to view video.

Groups then returned the their stations, recorded the mass, and then put a cap over the flask, flipped over the flask, and saw the chemical reaction between the white substance and the blue liquid. The result of the chemical reaction was a white solid that formed. Groups then went on to find the mass of the flask with all its components and record their results.

When students finished, they went back to their desks and Mr. H began to pass out scan-trons for our pop quiz. The quiz was only 14 questions, and consisted of the material learned in chapters 1:1-2. The quiz lasted untill the end of class.

Tuesday, September 14

Today we started class with checking our answers for the 1.2 measurements reading sheet (packet pages 19&20). Next, we went over and completed problems 13, 14, 15, and 17 in our unit packets on page 7. These problems were measurements of volume which consists of cubic meters/centimeters, milliliters and liters. We were introduced to a new theory stating that 1 cm cubed=1 mL. That piece of information was key to solving these four problems.

This is my work for the problems above:

After going over and completing those problems on page 7, we were introduced to scientific notation. This can be located on packet page #8. Scientific notation, aslo known as exponential notation, is a way of writing numbers that accommodates values too large or small to be conveniently written in standard decimal notation. On this packet page we converted numbers from standard decimal notation to scientific notation, and then we converted from scientific notation to standard decimal notation. When converting you need to keep in mind that the rule of significant figures still applies. A helpful website for understanding scientific notation is:

http://en.wikipedia.org/wiki/Scientific_notation

When converting, you always write the notation with the FIRST NONZERO NUMBER. (decimal) REST OF SIGNIFICANT FIGURES FOLLOWING *(times) 10 to the Xth power. To determine the exponent (x), you count how many spaces you have to move the decimal (right or left) in order to reach that first nonzero number. If the exponent is positive, that means there is a larger number with numerous zeros after it and you will be moving the decimal point to the left. If the exponent is negative, it would be a very small number and you have to move the decimal point to the right.

If you are trying to convert the numbers from scientific notation to the standard decimal notation, you have to move the decimal place and then fill in zeros. If there is a negative exponent, you will move the decimal point to the left ____ spaces. If there is a positive exponent, you will move the decimal point to the right ___ spaces. Like I said before, significant figures are still in effect for these problems.The last section (3) on page 8 in the unit packet is practice using scientific notation on a calculator. When entering the operations on the calculater, you have to make sure to include all parentheses in order for the answer to come out correct. There is a special "EE" button on the CAS calculators especially for scientific notation. After getting an answer on the calculator, you were then to put those answers back into scientific notation, but more simplified than the original.

The last thing we talked about in class was chemical and physical properties. A chemical property is a property of a substance which describes how the substance interacts (reacts) with another substance. A physical property is a property of a substance which describes the substance without describing its interaction with other substances. This was followed up by a demo lab where Mr. Henderson heated a colorless test tube over a methane burner. The test tube then turned a purplish color and took solid iodine and changed it to a gaseous iodine. This was used during the process of sublimation which includes freezing, melting, boiling, etc.

Here is a link to an interactive website to help you understand the difference between chemical and physical properties:

http://www.teacherbridge.org/public/bhs/teachers/Dana/chemphys.html