Test Tomorrow Over Electrochemistry

Below is the key to the review for the oxidation / reduction unit. Also included are images of the quiz that was given on Friday, December 10th and the solutions. The test tomorrow will be a combination of mutiple choice and short answer.

More Balancing Complex Redox Reactions Practice

On the Events Calendar for the class website, I have posted a pdf file of five more practice problems for balancing complex redox reactions. Below is the key for the five problems. On Monday, we will be reviewing all hour. Any questions that you may have can be addressed then.

Key - Balancing Complex Redox Reactions

Below are the solutions to the Balancing Equations (Redox Method)

Balancing Complex REDOX Reactions

A VODCast covering how to balance a complex REDOX reaction has been posted on the Events Calendar of the class webpage. It is a Quicktime movie file, so you will need the Quicktime program to view it. The problem covered is number 5 from part C of the worksheet.

Chemical Reactions Test

Below is a solutions guide to the optional review for tomorrow's test on chemical reactions. Come and see me tomorrow morning if you have any questions.

Quiz Reminder

Tomorrow will be a quiz covering the following topics listed below.

• Balancing chemical reactions and classifying types of chemical reactions. You will not need to write chemical compound formulas from names and then balance the reaction. You have your "Balancing Chemical Reactions" worksheet to study from.
• Using a solubility table. You will be given a name of a compound or a compound formula and then be asked to determine if the ionic compound is soluble (aqueous) or not soluble (solid).
• Using an activity series table. You will be given balanced single replacement reactions and then asked if the reactions could happen based upon the activities of the single element and its like element in the compound.

You will be able to use your owm periodic table and you will be supplied with a new solubility table / activity series table. The quiz grade will be going is the "Assessment" category of your grade.

Balancing Chemical Reactions

For those of you experiencing a little difficulty on the balancing chemical reactions worksheet, I have some advice for a possible sticking point.

Elements combine in whole number, that we know to be true. Thus, we need to have the smallest whole number ratio of the coefficients used to balance the equation. To balance an equation initially, you may use a fraction, but then you must modify the coefficients to make them whole numbers. Below is an example.

Reaction: C3H6O2 + O2 --> CO2 + H2O

Hint: Wait to balance oxygen last since placing a coefficient in front of elemental oxygen (O2) will not change any other elements.

Initial balancing: C3H6O2 + ?O2 --> 3CO2 + 3H2O

The carbons and hydrogens have been balanced. All that is left are the oxygens. There are a total of 9 oxygens of the product side (right of the arrow). Notice that 2 oxygens exist in the compound on the reactant side. Thus, to balance out the oxygens, an equation can be set up.

2 + x = 9 --> x = 7 --> Seven oxygens are required to balance the reaction, so this dictates that we use a coefficient in front of oxygen (O2) that will produce 7 oxygens. This will cause a coefficient of 3.5 to be used. This is not a whole number, but we can deal with that later.

Almost balanced: C3H6O2 + 3.5O2 --> 3CO2 + 3H2O

Having a fraction as a coefficient is not allowed, thus we must convert 3.5 to a whole number. To accomplish this, we will multiply 3.5 by 2. Just like in algebra, if something is done to one number, we must do the same thing to all of the numbers. Thus, all coefficients will be multiplied by 2. Doing this keeps the equation balanced.

Almost, nearly balanced: 2(C3H6O2 + 3.5O2 --> 3CO2 + 3H2O)

BALANCED!! 2C3H6O2 + 7O2 --> 6CO2 + 6H2O

Make sure that you check all of the elements on each side of the reaction to ensure that is has been balanced correctly.

Chemical Compound Remedial Work

If you would like more practice for the writing chemical compound formulas and chemical compound names quiz that will be given on Wednesday, November 3rd, 2010, a remedial quiz has been posted as a .pdf file on the Events Calendar on the class web-page. You can take the quiz and then check your results against the key for the quiz that has been given below. To mimick the quiz conditions as closely as possible, give yourself only 15 minutes to complete the quiz.

Writing Compound Names and Formulas Key

Below are the keys to the writing chemical formulas and compound names packet. On Monday, November 1st, you will have a diagnostic quiz to test your ability to write chemical formulas and names of chemical compounds. The diagnostic quiz will go in your homework grade. On Wednesday, November 3rd, you will have another quiz on the same material, but that grade will go in your assessment grade. Please make sure that you address any problems that you may have with the material by Wednesday.

Corrections: #18 on 'Naming Ionic Compounds' worksheet should be magnesium nitrite and #20 should be bicarbonate and not bisulfate.

Chapter 4 and 18 Test

The practice test for Chapters 4 and 18 is on the Events Calendar of the class webpage. It is a pdf file and at the end is a key. If you have any questions, I will be at school early tomorrow morning, so stop by and see me.

Not all of Chapter 4 and 18 will be tested on. In Chapter 4, we have not discussed compound formulas or the periodic table in depth, therefore do not concern yourself with sections 4.4 and 4.8 through 4.11. In Chapter 18, do not concern yourself with section 18.5. All other sections in both chapters are open for questioning. Concern yourself with what was presented in the note packages and work sheets given in class. Make sure that you review the part of the unit dedicated to radon.

Chapter 3 Test-Short Answer-Remedial Session

The remedial sessions for the short answer portion of the Chapter 3 test will be held at the following times. After school on Tuesday, October 5th, from 2:25 pm to 2:55 pm OR before school on Wednesday, October 6th, from 6:45 am to 7:15 am. You only need to attend one of the two sessions to earn back half of the points that you missed on the written portion of the exam.

Prepare for your test!

Test tomorrow. I will be at school by 6:00 a.m., so if anyone wants to see me, I will be in my room.

Remedial Information and Calorimetry WS Solutions

First, a reminder about the remedial session being offered to earn back one third (1/3) of the points that you lost on the Chapter 2 unit exam. The times will be at 6:30 a.m. to 7:15 a.m. OR 2:25 p.m. to 3:10 p.m. on Friday, September 24th, 2010. The remedial sessions will be held in the third floor lecture hall. You must be present for the entire time and you must participate and turn in a completed packet that will be given out at the beginning of the session. No exceptions!!

As promised, I have made a VodCast of solutions to two of the problems from the Calorimetry worksheet. The problems are numbers five and eight. The solution to number eight is very similiar to the solution to number six, which was begun in class. The movies are .mov, so you will need Quicktime to play them. The file can be found by going to the class website and on the Events Calendar under the date September 22nd, 2010 is a link to the file. The total running time is just over two minutes, so if you do not catch part of the problem because it is going to fast, just hit pause and back up. Come and see me if you have any questions about any part of the worksheet.

Dance The Night Away!!

I hope that everyone enjoyed the little dance lesson offered in class today. Remember, when I D.J. the homecoming dance, I had better see all my students movin' and groovin'. Let's review the parts of the "Molecular Motion / States of Matter Dance" or if you prefer "States of Matter / Molecular Motion Dance".
Part 1 - "The Solid" - Fists together and an ever so slight motion showing the molecules vibrating. The fists cannot move around one another nor can they move apart from one another. This shows the "vibrational motion" that all solid molecules have when subjected to energy.

• Definition - Energy - the ability to cause change. Changing the position of a molecule due to movement requires energy.

Part 2 - "The Liquid" - Fists are still touching one another, but they can now move around each other in a circular motion. Vibrational motion is still retained and movement of the fists around each other illustrates the "rotational motion" now afforded to the molecules. Rotational motion is achieved because enough energy is absorbed by the material to cause the vibrational motion of the solid to become so intense, the bonds that once held the molecules in place as a solid are broken.

• Definition - Temperature - the direct measure of molecular motion. A substance's melting point (solid to a liquid; vibrational motion to rotational and vibrational motion) is the molecular motion rate (temperature) that causes the bonds between the solid particles (atoms, molecules) to be broken.

Part 3 - "The Gas" - Fists are no longer touching and are moving in all directions in three dimensional space. Vibrational and rotational motion are still retained and the movement of the fists in all directions illustrates the "translational motion" now afforded to the molecules. Translational motion is achieved because enough eneryg is absorbed by the material to cause the rotational motion of the liquid to become so intense, the bonds that once held the molecules together as a liquid (touching, but able to move around each other) are broken.

• Analogy - "The Mean Uncle" - You are at a family outing and you are a young child. You go to your uncle, "Please swing me!" Your uncle abliges you, but before he grabs your hands to swing you around in a circle, he puts grease all of you hands and arms and his hands and arms. As he spins you round and round and picks up more speed, the weak bond that exists between you and him (greasy hands) is broken quite easily. You end up flying off into a bush. This is just like a liquid. The molecular motion becomes so great (high enough temperature), the bonds holding the liquid molecules together are broken and a gas is formed.

Just as energy can be placed into a material to increase molecular motion and break bonds, thus changing states of matter, energy can be removed (or lost) from a material. As energy is removed, the molecular motion decreases. The decreased molecular motion does not allow the particles (atoms or molecules) to overcome the attractive forces between them, thus bonds are formed between the particles.

**Molecular motion exists as long as there is energy in a system. Extra credit to anyone who comes to class tomorrow (Wednesday, September 15th, 2010) with the name of the concept where no energy exists, thus no motion exists in matter. Please write your name, period and the name of the concept on a piece of paper and hand it in at the beinning of your class period.

Homework Assignment

Please complete the following for class on Tuesday, September 14th, 2010. Read pages 55 through 66 (Sections 3.1 - 3.5) in Chapter 3 of the textbook. On pages 75 and 76, please answer questions (problems) 13, 14, 18, 20, 21, 27, and 28).

Test on Friday, September 10th, 2010

Below are the major topics to be covered on the test tomorrow, Friday, September 10th, 2010. You have all of your packets, quizzes, and worksheets back to study from. The material below is from mainly from Chapter 2 in the book, though the book was used very little during the time spent covering the material. This is your first major assessment of the semester, so this will be the most important score towards your overall grade, so please put forth an effort to do well.

Dimensional Analysis - Assessment Reminder

First, tomorrow (Friday, September 3rd) is your first assessment of the semester. As stated in the previous post, you will be performing a lab practical based upon the Density of Pennies lab. All practices associated with that lab will be assessed.

• You will be required to find the density of a material accurately.
• You will be given roughly 15 minutes to collect data in the lab area by yourself.
• There will be no lab partners involved, so you must know how to operate and read all lab equipment used.
• Your procedure must maximize the number of significant figures in each measurement.
• Your procedure must minimize error, thus the order in which measurements are made must be considered. *Note, you will not be required to record the steps of your procedure. Doing steps in the wrong order will cause your calculated value for density to be inaccurate.
• Masses must be found to the 1/1000 of a gram and the volumes to the 1/10 of a mL.
• You must present your measurements in a Data Table in a neat and orderly manor. You will lose points for not including the units associated with each measurement. *Do not perform any calculations of substance (i.e. density) in the data table. You can calculate the mass and volume of the material by subtracting an initial amount from a final amount. That is the only type of calculation allowed in a data table.
• When calculating the density, significant figure rules MUST BE FOLLOWED!!
• If you do not include units in your final calculated value, you will lose points.
• Every year, a student or two forgets the most basic part of the lab, and that is how to find density. Please remember that it is mass divided by volume. If you have to be reminded, you will lose points.
• Finally, you will be asked to read a scenario based upon a lab procedure and ask questions associated with knowing proper lab procedure and calculation procedures involving measurements. You will need to answer most of the questions in complete sentences.

**Rules For Performing Dimensional Analysis**

1. Start out with what you know. (Or put another way, what value is given in the problem.)
2. Set-up what you know as a fraction if not already a fraction.
3. Find the correct conversion factor (or factors) needed to convert from one unit to another.
4. Set-up the conversion factor as a fraction so the unit(s) that are not desired factor (cancel) out and the desired units remain.
5. Perform the needed calculations. Almost all conversion factors will be treated as absolutes (counted numbers are absolutes), so the conversion factors should not affect significant figures. THE NUMBER OF SIGNIFICANT FIGURES STARTED WITH IN A CONVERSION IS HOW MANY SIGNIFICANT FIGURES THE ANSWER SHOULD HAVE!

The rule written below in big, bold letters should always be applied to metric conversion.

**Always convert to the base unit!!**

The base units for the metric system are meters (m) for length, liters (L) for volume, and grams (g) for mass. A copy of the conversion table given out in class can be found on the Events Calendar under the date September 2nd. A copy of the conversion packet can also be found on that date.

Over Due Update

It has been since Saturday morning that I posted anything of substance. Let's recap the first part of this week.

• Monday - a short quiz was given to assess your understanding of significant figures and and why they are important and how/why they are used in calculations. Please make up the quiz if you have not taken it yet. We also discussed the formal lab report as it related to the Density of Pennies Lab. You were given a copy of a lab report that showedd the good points of what you should strive for in a formal lab report and also some "do not do" parts that will cost you points in later formal lab reports. Use it as your guide as we do lab reports throughout the year.
• Tuesday - we discussed graphing and introduced the use of the graphing calculator as a tool for the class. We went over how to enter data in the calculator, set up a plot (graph), and performed a linear regression on the data. We discussed how the values in a linear regression can be used for density determination and accuracy of density determination.
• Wednesday - we continued with the discussion of the linear regression and its use. We introduced the concept of the correlation coefficient (r^2) and a tool for rating consistency of data. You were given a worksheet (Data Analysis Worksheet) that needs to be completed for tomorrow. It requires you to apply the concepts discussed in class of using the information from a linear regression and graph to assess consistency and accuracy of data. You will not be held accountable for the operation of a calculator this semester (you will 2nd semester), but you will be held accountable for your ability to analyze data. Please have the six questions to the Data Analysis Worksheet answered for tomorrow.

Tomorrow (Thursday, 9/2) we will go over the Analysis Worksheet and I will be collecting it. We will breifly discuss your first assessment (test) of the semester, which will be given on Friday. It will be a lab practical. You will be asked to find the density of a material and you will be expected to follow all procedures/rules for measurement and calculations. Your ability to determine the actual density will be graded, so you must be accurate in your measurements. We will start a new packet tomorrow. Expect a major unit exam next week.

GRADES HAVE BEEN UPDATED!!!

I have just updated grades. Some individuals are missing minor assignments (like the signed Lab Safety Contract and Class Policies and Procedures), but because there are very few grades to buffer a bad grade, those individuals have very poor (I'm talkin' "F"!!) grades. Please look at your grade and get the required material to me. The Lab Safety Contracts and Class Policies and Procedures can be found on my teacher pages. I think that activities start taking grade reports this Wednesday for eligibility, so the sooner the better for rectifying the situation.

Density of Pennies Lab and a Movie

Remember, the write-up for the Density of Pennies lab is due at the beginning of class on Monday, 8/30/2010. It must be either written out neatly or typed (just a hint, typing pleases me and I may be kinder when grading). Please follow the seven step format of the Formal Lab Report sheet that you were given last Thursday. Please look over the pointers that I have bulleted below:

• We have covered the Purpose and Theory statements in class, so I am not going to address those points again.
• Be short and to the point on your procedure. The following is a good example of the amount of detail that you should include for a particular step. "Found the mass of pennies and weighing dish to the 1/1000 of a gram. Repeated this step for both categories of pennies."
• The Data Table should easy to follow and include all units of measurement. Do not perform calculations (other than a final measurement being subtracted from an initial measurement) in the data table.
• Sources of Experimental Error (SEE's) should address matters of procedure or technique that may cause measured values to be slightly inaccurate. These need to well developed ideas, so a paragraph may be needed to completely explain an event that would cause error to be introduced into measurements taken during the lab. You could have multiple SEE's associated with a lab.
• Your Conclusion MUST address if the Theory used was able to achieve the Purpose. An example could be: "The densities for both penny categories only differed by one tenth of a gram per milliliter. Do to uncertainty of measurement, I do not feel that it is proper to declare that there is a definite difference in how the pennies were manufactured (minted) prior to 1982 and after 1982." Also remember, you must always include a statement on how you would improve the lab if given the chance to do it again.

Please click on the link Density Lab. I have made a Vodcast (not Podcast) of a fictitious scenario that will hopefully illustrate to you an emphasis that I made to you about having as large sample as possible. The Vodcast also addresses points to the write-up. It is hosted on a website called "TeacherTube". You may have to sign up for "TeacherTube" prior to watching the video. Please be prepared to answer questions (maybe in the form of a quiz) that relate to the lab on Monday. Have a good weekend.

Lab Tomorrow and Extra Credit Opportunity

Tomorrow you will be performing your first "official" laboratory experience for a grade. Your only expectation for preparing for the lab is to write a Purpose statement for the lab and to also write a Theory statement. Remember, you are going to try and confirm if the minting (manufacturing) process for pennies changed in 1982. You are going to use the physical property of density to distinguish the different categories of pennies. Since you will be measuring in this lab, you MUST incorporate precision and accuracy of measurement and proper use of precision and significant figures in calculations. The validity of your results depends upon it.

**Extra Credit Opportunity** If you bring in a 4-pack of AAA batteries, you will receive 10 points extra credit towards your homework portion of your grade. The purpose of me (Mr. Brueckner) stockpiling batteries is two fold. First, it supplies the calculators that I allow students to use in class with batteries. Second, it provides a stockpile of batteries for any and all students enrolled in any of my classes to have a source of batteries if the batteries run out in a student's personal calculator. Remember, I do not offer extra credit on an individual basis, so take advantage of any and all extra credit opportunities when offered. You can bring batteries in through September 3rd. Have a good night.

Liar, liar, pants on fire!!

People probably left class today feeling very much confused as to why I called everyone a liar in class when the results of the area of the science department were displayed. Now, don't feel offended if I called you a liar, I do not think ill of you. I do take issue with almost everyone's reported area value. Below I will explain why.

First it has been established that every measurement has uncertainty built into it due to the estimation of the last digit of any measurement. Also, the nature of the procedure introduces error. Since the measuring stick (a.k.a "The Brueckner") had to be slid along the floor end to end over 25 times, it is inevitable that the length measurement will be off by not starting at the precise location that the last measurement ended. This and many other errors could be found in your technique. This is why we never say the "E" word when discussing measurement.

You used two length measurements (which both contained uncertainty and probably error) and multiplied them together. Not only did you multiply the magnitude of each measurement, you also muliplied the error of each measurement by over 25 times. Therefore, any group that reported an area meausurement with more decimal places than what was originally present in the measurement cannot guarantee that calculated value.

These are example from 7th hour:

27.6 B x 32.7 B = 902.52 B^2 --> This should have been reported as 903 B^2
29.63 B x 25.90 B = 767.417 B^2 --> This should have been reported as 767.4 B^2
30.025 B x 26.087 B = 783.262175 B^2 --> This should have been reported as 783.26 B^2

All measurements from the above examples are correct. All groups used the correct amount of precision in the length and width measurements. I will discuss the rule that needs to be followed in class tomorrow, but can you deduce the rule from the values that I indicated to be the correct values to report?

Significant Figures vs Place-holder Zeroes

Today we went into a number of different scenarios on when numbers are significant (the certain digits and one uncertain digit of a measurement) and when zeroes are not significant (only placeholders). If you understand the intent of the author of the measured value, you can determine what is significant to the measurement and what is needed only for the magnitude of the number. There are a bunch of rules in Chapter 2 of the book on how to determine significant figures and you are free to use them for significant figure determination, but in my opinion, if you understand the intent on how a measured value was written, you will have an eaier time of significant figure dtermination. Significant figure determination is extremely important once we start using measured values in calculations. This will be covered tomorrow (Tuesday, 8/24) and Wednesday, 8/25.

You should finish through significant figure determination, #15 for tonight. We will go over the solutions first thing tomorrow. Please see me if you have any questions on the material.

Measurement Readings (Cont.) and Error (Systematic vs. Random)

We started the day by reporting the mass values measured the day before on the 4-beam balance. Part of the discussion dealt with systematic error (when an error occurs over and over consistently) and random error (an infrequent, singular event). Example, the fact that the 4-beam balance does not zero is a systematic error. It is consistent as long as you use the same scale, that is why I insisted that you go back to the same lab area that you used the day before so you used the same scale. You kept the systematic error the same because of it. Your data MAY be slightly inaccurate, but you are consistent. If you had changed scales, you would be introducing random error. You values would vary due to different reasons (in this case a different scale). Therefore, there would be no consistency in error and you could not factor out the error because it would be constantly changing, thus a different fix would be needed each time.

Please finish the graduated cylinder (volume) readings and thermometer readings (temperature) on the packet for tomorrow.

Measurement_Precision_And Why We Will Never Say The "E" Word

Today we covered quantitative (measured) data collection. This type of data would include mass, length, volume, time, etc. We discussed precision and the limitations of measurement. We discussed the uncertainty associated with all measurements because of the estimation of the last digit of all measurements. For this reason, it is not proper to say the word "exact" when discussing a measurement. Exact implies that you can guarantee the measurement without any question. The problem with making that type of guarantee would be if another individual made the same measurement with a more precise instrument and found a value different than what you reported, you would be liable for guaranteeing the value. This is an extreme example, but you should use a term like precise. That gives you some wiggle room.

When can you say "exact"? Believe it or not, you can. When counting, you can say exact because there is no question that you have ten toes or 96 french fries (as long as you are careful counting).

Please finish the first page of the measurement worksheet tonight for homework. The page covers how to read 3 and 4 beam scales (balances). We will go over it first thing tomorrow. Please bring with you the piece of paper that has the mass of the card found in class today.

Chapter 2 Overview

Your only assignment for tonight is to go over chapter 2 in the book and do a self assessment of material in each section of the chapter. On a piece of paper, write the section number (example-2.2) and just answer if you are familiar with the material or not. Examples: Yes, I know this. No, I have seen this but I do not remember it. No, I have never seen this material before. I just want an idea of what individuals are comfortable with.

First Day of Class

Welcome to Mr. Brueckner's chemistry class. I hope that we have a really good year together. You need to complete the following by Friday, August 20th, 2010.

1. Print a copy of the Classroom Policies and Procedures found on Mr. Brueckner's Chemistry page. The copy needs to be signed acknowledging that you and your parent(s) / guardian(s) are aware of class expectations and grading policies.
2. Print a copy of the Lab Safety Agreement, which can be found on Mr. Brueckner's homepage. The agreement must signed by you and your parents. Read over the safety contract and be prepared for a 20 question lab safety quiz on Friday, August 20th, 2010.