Chapter One, Section One


OBJECTIVES

  1. Learn the different changes that can occur in matter
  2. Learn the scientific method
  3. Learn how to use scientific (or exponential) notation

I . INTRODUCTION

Chemistry is the study of matter, which is anything that has mass and takes up space. Specifically chemistry studies the forms and properties of matter and it studies the transformations and interactions of matter.

There are two classifactions for changes of matter:

II. THE SCIENTIFIC METHOD

We must have a systematic method for studying physical or chemical properties. This method is called the scientific method. Using the scientific method we observe some facts (anything that can be experimentally observed under controlled conditions), make a hypothesis to try to explain the facts, test the hypothesis, modify the hypothesis depending upon the test results, etc. Once we have an hypothesis that explains the facts within experimental error we can then state our hypothesis as a theory. Note that a theory never becomes a fact. Facts are what can be experimentally observed and a theory is an explanation of the facts. New facts could invalidate the theory, and many theories have been so invalidated over the years. Therefore we must never treat a theory as if it were the final explanation. We can use the theories to help us study matter until new facts invalidate the theory.

III. EXPONENTIAL NOTATION

We could say that a biggg rock weighs 35600000000000000000000000 pounds. Or we could use exponential notation to say that the rock weighs 3.56 x 1025 pounds. We could also say that a small particle weighs 0.00000000000000000000000000000000000283 pounds. Or we could say that the small particle weighs 2.83 x 10-36 pounds. If we work with very small or very large things then you can see the importance of using such a method to express the numbers. To properly use the notation, we will always have only one digit to the left of the decimal point. The 2.83 or the 3.56 are called the coefficients and the 25 or the -36 are called the exponents. Since anything to the zero power is zero, 100 = 1.

This method of writing numbers is also called scientific notation.

If we want to add or subtract two numbers express in scientific notation we must first make sure that they both have the same exponents. For example to add 2.56 x 102 and 3.65 x 103, we can change 2.56 x 102 to 0.256 x 103 and then we can add them to get 3.906 x 103. Alternatively we could have changed 3.65 x 103 to 36.5 x 102, added and obtained 39.06 x 102 and then changed the answer to exponential notation and we would have 3.906 x 103.

If we want to multiply two numbers expressed in scientific notation then we multiply the coefficients and add the exponents. For example 2.56 x 102 multiplied by 3.65 x 103 gives 9.344 x 105. I can hear some of you saying why don't I just put the numbers in my calculator and press "x"? Well you need to know how the process works and then once you understand that you can use your calculator.

If we want to divide two number expressed in scientific notation then we divide the coefficients and subtract the exponents. For example 3.65 x 103 divided by 2.56 x 102 would be 1.43 x 101. Similarly 2.56 x 102 divided by 3.65 x 103 would be 0.701 x 10-1 or 7.01 x 10-2 in scientific notation. Note that I have expressed the answer in the same number of digits as in each of the given numbers -- more about that later.

ASSIGNMENTS

Now you need to practice doing problems relating to the above concepts.

QUIZ ONE

After you have studied this material and practiced some problems, take quiz one. If you score at least 80 on the test then you are ready to continue to the next section.


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Web Author: Dr. Leon L. Combs
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