✔ Online practice and study aids: The online practice that comes free with this book offers 1,001 questions and answers that allow you to gain more practice with chemistry concepts. The beauty of the online questions is that you can customize your online practice to focus on the topics that give you the most trouble. So if you need help with moles or balancing reactions, just select those question types online and start practicing. Or if you’re short on time but want to get a mixed bag of a limited number of questions, you can specify the number of questions you want to practice. Whether you practice a few hundred questions in one sitting or a couple dozen, and whether you focus on a few types of questions or practice every type, the online program keeps track of the questions you get right and wrong so you can monitor your progress and spend time studying exactly what you need.
To gain access to the online practice, all you have to do is register. Just follow these simple steps:
1. Find your access code.
● Print-book users: If you purchased a hard copy of this book, turn to the inside of the front cover to find your access code.
● E-book users: If you purchased this book as an e-book, you can get your access code by registering your e-book at www.dummies.com/go/getaccess. Simply select your book from the drop-down menu, fill in your personal information, and then answer the security question to verify your purchase. You’ll then receive an e-mail with your access code.
2. Go to http://learn.dummies.com and click Already have an Access Code?
3. Enter your access code and click Next.
4. Follow the instructions to create an account and set up your personal login.
Now you’re ready to go! You can come back to the online program as often as you want – simply sign in with the username and password you created during your initial registration. No need to enter the access code a second time.
Tip: If you have trouble with your access code or can’t find it, contact Wiley Product Technical Support at 877-762-2974 or go to http://wiley.custhelp.com.
Where to Go from Here
Where you go from here depends on your situation and your learning style:
✔ If you’re currently enrolled in a chemistry course, you may want to scan the table of contents to determine what material you’ve already covered in class and what you’re covering right now. Use this book to help you with the new stuff and review the old stuff.
✔ If you’re just beginning a chemistry course, you can follow along in this book, using the practice problems to supplement your homework or as a study tool for the test. Alternatively, you can use this book to preview material before you cover it in class. The book is designed to mirror your class about as well as it can, though every teacher has a preferred order for covering material. You may need to jump around a bit, but the book is designed for this.
✔ If you bought this book a week before your final exam and are just now trying to figure out what this whole “chemistry” thing is about, well, good luck. The best way to start in that case is to determine what exactly is going to be on your exam and to study only those parts of this book. Due to time constraints or the proclivities of individual teachers/professors, not everything is covered in every chemistry class, so make sure you know what to study!
No matter the reason you have this book in your hands now, there are three simple steps to remember:
1. Don’t just read it; do the practice problems on your own and without help.
2. Don’t panic.
3. Do more practice problems.
Anyone can do chemistry given enough desire, focus, and time. You aren’t going to be the exception to that rule. Just keep at it, and you’ll be fine.
Part I
✔ Discover how to deal with, organize, and use all the numbers that play a huge role in chemistry. In particular, find out about exponential and scientific notation as well as precision and accuracy, and use significant figures to express the accuracy of measurements and calculations.
✔ Convert many types of units that exist across the scientific world. Use the factor label method to accurately and easily perform these conversions. Calculate the density of substances and look at derived units.
✔ Determine the arrangement and structure of subatomic particles in atoms. Examine the history of atomic discovery and the importance it plays in science today. Protons, neutrons, and electrons play a central role in everything chemistry, and you find their most basic properties in this part.
✔ Get the scoop on the arrangement of the periodic table and the properties it conveys for each group of elements. Just from looking at the periodic table and its placement of elements, you can find so much information, from electron energy levels to quantum numbers, ionic charge, and more.
Chapter 1
Looking at Numbers Scientifically
In This Chapter
▶ Using scientific notation
▶ Comparing accuracy and precision
▶ Using and calculating with significant figures
Like any other kind of scientist, a chemist tests hypotheses by doing experiments. Better tests require more reliable measurements, and better measurements are those that have more accuracy and precision. Accurate and precise calculations are essential to successful experiments, so a large chunk of chemistry centers on ways to report and describe measurements.
How do chemists report their precious measurements? What’s the difference between accuracy and precision? And how do chemists do math with measurements? These questions may not keep you awake at night, but knowing the answers to them will keep you from making mistakes in chemistry.
Using Exponential and Scientific Notation to Report Measurements
Because chemistry concerns itself with ridiculously tiny things like atoms and molecules, chemists often find themselves dealing with extraordinarily small or extraordinarily large numbers. Numbers describing the distance between two atoms joined by a bond, for example, run in the ten-billionths of a meter. Numbers describing how many water molecules populate a drop of water run into the trillions of trillions.
To make working with such extreme numbers easier, chemists turn to scientific notation, which is a special kind of exponential notation. In exponential notation, a number is represented as a value raised to a power of 10. The decimal point can be located anywhere within the number as long as the power of 10 is correct.
Suppose that you have an object that’s 0.00125 meters in length. Express it in a variety of exponential forms:
All these forms are mathematically correct as numbers expressed in exponential notation. But in scientific notation the decimal point is placed so that only one digit other than zero is to the left of the decimal point.