Instructor's Notes to On-line CH104 Class

This is the place where your instructor will leave notes about a variety of things, like when the lab materials for a lesson will be taken down, the last date to turn in homework, etc.  The first section will be a place for current bulletins/items of immediate concern, with general notes for each week following that section.

Week 1 Notes: 

This week you will attend lab the first time and pick up your workbook (which contains your lab instructions, objectives, sample exercises, etc.) and problem sets for the term. 

This week is special as it covers two sections, both 1a and 1b. 

 Section 1a covers significant digits and scientific notation.  While there are no required assignments to turn in from Section 1a, do not ignore this section!  Significant digits, and scientific notation are very important and you will be using (and be graded on) them throughout the term.  Points will be deducted for showing too many (or too few) significant digits on all quizzes and tests.  Scientific notation must be understood to do the math. 

Section 1b covers "Lab Fundamentals – I: Physical Properties."  Note that only part of the lab from this section needs to be turned in.  The concept of density is also introduced and you will need to use some algebra with the basic equation: 

            Density = Mass/Volume; Units are usually grams/mL

 Remember, for example, when you calculate volume, the units should come out in volume units (e.g., mL) instead of something like gram-centimeters!

 Some areas where students have had problems with these sections in the past require: 

- Paying attention to the "Objectives" and "Assignments" that are listed in the workbook at the beginning of each section. 

 -  Reading the laboratory measurements to enough significant digits.  For volume and temperature measurements, you get your last significant digit by estimating between lines, so you end up with 3 digits independent of where the decimal point is. 

 -  Realizing that there are two different methods for using significant digits – one for multiplication & division and another for addition & subtraction.

 -  Knowing how to use scientific notation on their calculators. 

 -  Showing the correct significant digits in their answers.  If you start with 25.432 g and 41.6 mL, your calculator may show a density of 0.611346154 g/mL but not all of these digits are significant. This is a division problem, and the volume only has 3 significant digits, so the answer should be rounded to 0.611 g/mL.

 Remember to keep up with your work as it is very difficult to catch-up if you get behind.  Further, labs are torn down each week to make room for the next lab.  Also, you will lose points that are needed for your grade!

-Eden Francis, 9/19/07

Chem 104 Week 2 Notes:

10/7/08 - Eden's office hours are posted in the online syllabus.

 In addition to the web materials, there are six Authorware modules that need to be covered.  If you purchased the Authorware CD (available from our lab for $5), you will find these modules as follows: 

 These files are already installed on the CCC lab computers and run seamlessly from the Chem-104 web site.  If you have not purchased the CD, you may download the files (2-3 megabytes each) from the CCC web site, install Authorware, and run them at home.  To run these files from the CD, open "My Computer."  Then, open the folder for your CD-ROM (containing the Authorware CD) then double-click on any of the above modules.

 The main lab experiment that you do this week is exercise 20 on page 19 of your workbook.  In fact, this is the only part of the lab that you need to turn in.  Start with this exercise and use the "cooking" or "waiting" times of this experiment to do the rest of the lab work.  Note: Authorware module 403E.EXE explains how to do this lab.  However, note that the 20-50 cm of magnesium shown in the workbook is the correct amount to use for this experiment.

 My experience with this lab is that you need a very hot flame to get the magnesium to react.  Here, you need to have the tip of the blue cone at the bottom of the crucible rather than surrounding the whole crucible.  Don't be shy with the heat. 

 One of the calculations for this week is for getting % compositions.  You need to divide by total mass.  For a pure substance, this is the weight of the components of that substance.  For a salt in a solution (with water), remember to divide by the weight of both the salt and the water (which make up the solution).  Do not just divide by the weight of the water.

 P. L. Hanrahan, S. Eggling;   January 9, 2005

Week 3 Notes:

Note that you need to memorize the names, symbols, and be able to determine the position on the Periodic Table for a number of elements. These 36 elements are shown in #4 of the Week 3 Objectives sheet. You will need to know these throughout your coursework in chemistry. You will also be tested them on your next quiz.

· Be sure that you know how to identify "Periods" and "Groups" on the Periodic Table.

· Note that there is also other terminology to learn as shown in Exercise 2 on page 4 of this week's lesson.

· In memorizing your elements do not confuse:

K vs. P, potassium vs phosphorus; Co vs. Cu, cobalt vs. copper; Mg vs. Mn, magnesium vs. manganese; S vs. Na, sulfur vs. sodium; and Ag vs. S, silver vs. sulfur.

and these are just a few of the errors that you can make!

· In the week 3 experiment, you only need to derive the Molecular Weight of the unknown gases. Some students think they also have to identify the actual chemical identity of the unknown. This is impossible as some gases have virtually identical Molecular Weights (e.g., CO vs. N₂). Further, some of your unknowns may be mixtures of several gases.

- You may wish to brush up on your significant digits training. Many students are losing points by not showing answers with the correct number of significant digits. Over the length of the term, these errors can easily drop you down a grade level!

--Pat Hanrahan, January 17, 2005, Sue Eggling , March 23, 2007

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