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.