CHM 100 students! Your first test will be Friday, February 1^st!

Test covers

• Chapter 1
• Chapter 2
• Chapter 3: Sections 3.1 – 3.5 (The “matter” half of the chapter)

Test format

• Multiple-choice questions. Expect 20-25 multiple choice questions. These will be answered on Scantron sheets. Some of these may require calculations. This section is will be worth approximately 60 percent of the points on the test.
• Problems/fill-ins. Expect ten or so questions of this type. You should expect some unit conversions here, questions about significant figures, and perhaps some density or drug calculations. You’ll need to show your work on any question that requires a calculation to receive any partial credit. No work, no partial credit!

Study guides

You should be able to do all of the “bullet points” on the Chapter 1-3 study guides. Get the study guides by following the links on the right-hand side of this page, or click the links below.

• [Chapter 1 Study Guide]
• [Chapter 2 Study Guide]
• [Chapter 3 Study Guide] <– You’re only responsible for the “matter” parts of this one!

How to prepare for the test

• Start preparing well in advance of the test! Ideally, you have already been working on the study guides and practice problems. If not, start now. Do not expect to do well on the first test if you don’t start studying until Thursday night!
• Go through the study guides and [class notes] and make sure you can do each “bullet point” on the study guide. Some of these “bullet points” will be simple definitions, while others will require much more practice and work.
• Use the [practice problems on the web], the suggested practice problems on the study guide, and [the quizzes] to practice chapter 2 skills. To simulate the conditions on the test, try practice problems without textbook and notes. Don’t look at your textbook and notes unless you get stuck! When you can work the problems quickly and without resorting to looking in your book and notes, you are prepared.
• Learn your calculator! You will be using your calculator to solve
  problems on the test, and you should be comfortable with the buttons (like the “EE” button) before test day! (You’ve also got to remember to bring your calculator on test day!)

… and as always, if you have any questions, you’re welcome to post them here or drop by the office during [office hours].

We discussed how to determine whether molecules were polar or not based on their shapes. To be polar, a molecule has to

1. have at least one polar bond.
2. be shaped in such a way that all of the molecule’s polar bonds don’t cancel each other out.

Dichloromethane, CH₂Cl₂, might appear to be a nonpolar molecule at first glance. Depending on how we draw the Lewis structure, we might fool ourselves into thinking that the two C-Cl polar bonds in the molecule would cancel each other out. However, that’s not really the case. The chlorine bonds are not arranged in a way that allows them to cancel.

This rendering is arranged in the way we draw the molecule on our paper. The hydrogen and carbon atoms are in the plane of the screen, and the chlorine atoms are in front of and behind the screen. You can see that the molecule has a “chlorine side” and a “hydrogen side”, and thus is polar.

If you can’t see it, this rotated rendering below makes the “sides” more obvious.