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Transcript of Christopher G. Hamaker, Illinois State University, Normal IL © 2008, Prentice Hall Chapter 1...
Christopher G. Hamaker, Illinois State University, Normal IL© 2008, Prentice Hall
Chapter 1Introduction to Chemistry
INTRODUCTORY CHEMISTRYINTRODUCTORY CHEMISTRYConcepts & Connections
Fifth Edition by Charles H. Corwin
Christopher G. Hamaker, Illinois State University, Normal IL© 2008, Prentice Hall
Chapter 1 2
Chemistry, The Central Science
• Knowledge of chemistry is important to understanding the world around us.
Chapter 1 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.
Chapter 1 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
Chapter 1 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.
Chapter 1 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
Chapter 1 7
Significant Figures
Significant figures - all digits in a number representing data or results that are known with certainty plus one uncertain digit
Chapter 1 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
• 60.052 has five significant digits
Chapter 1 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.
• 0.0032 has two significant digits
Chapter 1 10
How many significant figures are in the following?
1. 3.400
2. 3004
3. 300.
4. 0.003040
Chapter 1 11
How Many Significant Figures?
Round off each number to 3 significant figures:
1. 61.40
2. 6.171
3. 0.066494
Chapter 1 12
correct answer 152.83 liters
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:
37.68 liters 6.71862 liters
108.428 liters 152.82662 liters
Chapter 1 13
)calculator(on 109688692.210255.2
)94.15(102.4 84
3
Which number has the fewest significant figures? 4.2 x 103 has only 2
The answer is therefore, 3.0 x 10-8
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
Chapter 1 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
Chapter 1 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
0.0534 = 5.34 x 10-2
Chapter 1 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
Chapter 1 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.