Lesson 2

 

Preliminary Information
Inference
Types of Change and Separation
Chemical Reactions
Authorware Download
Conservation of Mass
Stoichiometry
Limiting Reagents
Percent Composition
The Laboratory
Two More Laws
Wrap-Up

Lab Fundamentals - II:

Chemical Reactions and Weight Relationships

Introduction

(Beginning with Conservation of Mass, this lesson is done using Authorware.  You can download the modules to view offline by going to the Authorware Download page or you can view the modules online by clicking on each one. If you have not yet prepared your computer for using Authorware, follow the instructions on how to do that on the orientation page at http://dl.clackamas.cc.or.us/ch104-00/orientat.htm.  You can also purchase a CD with all of the Authorware modules for the whole term; these CDs are available in the lab for $5.)

Note: The workbook references in the Authorware portions of this lesson refer to the previous edition of the workbook. Add 6 to the example number to get the location of the example in the current edition on the workbook. 

    In this lesson you will study some of the fundamental principles which govern all chemical reactions - in particular, those which deal with mass. However, we will start with observing chemical reactions and what is involved with distinguishing between chemical reactions and physical changes.

    You will not be concerned with figuring out whether two chemicals react or, if they do, what products are formed.  Rather, given that information, you will learn how to predict the relative amounts of the various reactants and products that would be consumed or produced.  This is the area of chemistry known as stoichiometry.

    In the laboratory, you will apply the principles you have learned to determine the composition of a compound, just as an early chemist might have done.

    Much of this lesson involves using ratios and proportions.  The central idea is that if two quantities (in our case, masses of chemicals in a reaction) maintain a constant ratio to one another, then given one you can always determine the other - provided you know what that ratio is.  For example, if the number of shoes in a room is always twice the number of people, then given the number of people, you can always figure out how many shoes are in the room (and vice versa).    As you work through the lesson and its many examples, try always to keep clear in your mind what the two quantities are and what their ratio is.  If that much is clear, you should find the examples and problems become easy to follow and to work out.

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Clackamas Community College E-mail instructor: Sue Eggling
Science Department
19600 South Molalla Avenue
Oregon City, OR 97045
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1998, 1999, 2002 Clackamas Community College, Dave Arter and Hal Bender