1. Christopher G. Hamaker, Illinois State University, Normal IL
© 2008, Prentice Hall

2. Chemistry, The Central Science
Knowledge of chemistry is important to understanding the world around us.
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3. Modern Chemistry
Chemistry is a science that studies the composition of matter and its properties.
Chemistry is divided into several branches:
Organic chemistry is the study of substances containing carbon.
Inorganic chemistry is the study of all other substances that don’t contain carbon.
Biochemistry is the study of substances derived from plants and animals.
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4. Scientific Investigations
Science is the methodical exploration of nature followed by a logical explanation of the observations.
The process of scientific investigation entails:
Casual or conscious observation that lead to formation of question(s)
planning an investigation
carefully recording observations
gathering data
analyzing the results – Form additional questions or experiments
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5. The Scientific Method
The scientific method is a systematic investigation of nature and requires proposing an explanation for the results of an experiment in the form of a general principle.
The initial, tentative proposal of a scientific principle is called a hypothesis.
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6. Scientific Method, continued
After sufficient evidence, a hypothesis becomes a scientific theory. A scientific theory provides an explanation to explain the cause of the phenomenon supported by experimental results
A natural law is a measurable predictable relationship within a set of conditions. Natural law does not attempt to explain the cause of observable phenomenon
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7. Significant Figures
Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit
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8. Recognition of Significant Figures
All nonzero digits are significant
7.314 has four significant digits
The number of significant digits is independent of the position of the decimal point
73.14 also has four significant digits
Zeros located between nonzero digits are significant
has five significant digits
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9. Use of Zeros in Significant Figures
Zeros at the end of a number (trailing zeros) are significant if the number contains a decimal point.
4.70 has three significant digits
Trailing zeros are insignificant if the number does not contain a decimal point.
100 has one significant digit; 100. has three
Zeros to the left of the first nonzero integer are not significant.
has two significant digits
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10. Determining Significant
Figures
How many significant figures are in the following?
3.400
3004
300.
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11. How Many Significant Figures?
Round off each number to 3 significant figures:
61.40
6.171
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12. Significant Figures in Calculation of Results
Rules for Addition and Subtraction
The result in a calculation cannot have greater significance than any of the quantities that produced the result
Consider:
liters
liters
liters
liters
correct answer liters
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13. Rules for Multiplication and Division
The answer can be no more precise than the least precise number from which the answer is derived
The least precise number is the one with the fewest significant figures
Which number has the fewest significant figures? x 103 has only 2
The answer is therefore, 3.0 x 10-8
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14. Scientific Notation
Used to express very large or very small numbers easily and with the correct number of significant figures
Represents a number as a power of ten
Example:
4,300 = 4.3 x 1,000 = 4.3 x 103
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15. To convert a number less than 1 to scientific notation, the original decimal point is moved x places to the right, and the resulting number is multiplied by 10-x
The exponent x is a negative number equal to the number of places the decimal point moved
= 5.34 x 10-2
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16. Types of Uncertainty
Error - the difference between the true value and our estimation
Random
Systematic
Accuracy - the degree of agreement between the true value and the measured value
Precision - a measure of the agreement of replicate measurements
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17. Critical Thinking: Reactions with Oxygen
What do burning wood, rusting iron, and exploding gasoline have in common?
All three are examples of combustion.
Combustion is a chemical reaction of a substance with oxygen.
Rusting is slow reaction, burning is rapid reaction, and an explosion is instantaneous reaction.
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