Introduction to Chemistry
Chapter 1 - Introduction to Chemistry
Course Details
Instructor: Dr. Nelli McMillan
Course Code: CHEM 10013
Semester: Fall 2025
Learning Objectives
Understand simple chemical phenomena (differences among solids, liquids, and gases) at the molecular scale.
Explain the difference between inductive and deductive reasoning in your own words.
Use appropriate techniques to convert measurements from one unit to another.
Express the results of calculations using the correct number of significant figures.
Critical Materials
Definition: Critical materials are important materials that possess unique chemical and physical properties allowing them to play vital roles in technology.
Examples:
Lithium batteries
Wind energy
Electric cars
The Scientific Approach to Knowledge
Nature of Knowledge: The approach to scientific knowledge is empirical, based on observation and experiment.
Scientific Method: A process for understanding nature involving:
Observation
Formulation of hypotheses
Experimentation
Formulation of laws and theories
Hypothesis Revision: A hypothesis is revised if experimental results do not support it.
Model Alteration: A model is altered if predicted events are not supported by data.
The Classification of Matter
Definition of Matter: Matter is anything that occupies space and has mass.
Examples of Matter: Your textbook, desk, chair, and body are all composed of matter.
Classification: Matter can be classified based on:
State (Physical Form): Solid, liquid, or gas.
Composition: Molecules and atoms.
Properties of Matter:
Physical Properties: Mass, density, boiling point, color, viscosity, hardness, melting point, heat capacity.
Chemical Properties: Types of chemical changes a substance undergoes, including corrosion and combustion.
Physical and Chemical Changes
Physical Change:
Definition: Changes that alter only the state or appearance of a substance, but not its composition.
Identity of atoms or molecules remains unchanged.
Chemical Change:
Definition: Changes that alter the composition of matter.
Atoms rearrange, transforming original substances into different substances.
Example: Rusting of iron is a chemical change.
Questions for Consideration:
Is the melting of ice a physical or chemical change?
Is the burning of wood a physical or chemical change?
Is the digestion of a baked potato a physical or chemical change?
Precision and Accuracy
Accuracy: Refers to how close a measured value is to the actual value.
Precision: Refers to how close a series of measurements are to one another or how reproducible they are.
Types of Errors:
Random Error: An error that has equal probability of being too high or too low, leading to variability.
Systematic Error: Makes measurements consistently too high or too low, often due to biases or impurities in measurement apparatus.
Interpreting Observations
Inductive Reasoning: Begins with specific observations and generalizes to a broader conclusion.
Deductive Reasoning: Involves taking two or more assertions and combining them to derive a clear and irrefutable conclusion (e.g., "If A and B, then C").
The Units of Measurement
Importance of Units: Units are standard quantities used to specify measurements in chemistry.
Common Unit Systems:
Metric System: Used in most of the world.
English System: Used in the United States.
International System of Units (SI):
Based on the metric system.
The abbreviation 'SI' comes from the French phrase 'Système International d'Unités'.
Prefix Multipliers
Explanation: The SI unit system uses prefix multipliers that change the value of the unit by powers of 10, similar to scientific notation.
Example: The prefix "kilo" means 1000, or $10^3$.
The Kelvin: A Measure of Temperature
Kelvin Scale: An absolute scale assigning 0 K to the coldest temperature possible.
Definition of Absolute Zero: $0 ext{ K} = -273^{ ext{°C}}$ or $-459^{ ext{°F}}$; it's the temperature at which molecular motion virtually stops and lower temperatures do not exist.
Numbers and Significant Figures
Exact Numbers: Have an unlimited number of significant figures, such as:
Exact counting of discrete objects (e.g., 5 pencils, 12 eggs).
Integral numbers in equations or defined quantities.
Inexact Numbers: Any measured value that has limitations in precision.
Counting Significant Figures
Reporting Scientific Measurements:
Every digit in a scientific measurement is reported as certain, except for the last digit which is estimated.
Precision Dependency: The precision of a measurement depends on the instrument used.
Rules for Determining Significant Figures:
All nonzero digits are significant.
Interior zeroes (between nonzero digits) are significant.
Leading zeroes (left of the first nonzero digit) are not significant, aiding in locating the decimal point.
Trailing zeroes are categorized as follows:
Trailing zeroes after a decimal point are significant.
Trailing zeroes before an implied decimal point are ambiguous, advisable to use scientific notation.
Examples:
28.5 has 3 significant figures.
5.02 has 3 significant figures.
408 has 3 significant figures.
7.0301 has 5 significant figures.
1200 (ambiguous, requires clarification).
$1.2 imes 10^{3}$ has 2 significant figures; $1.20 imes 10^{3}$ has 3 significant figures; $1.200 imes 10^{3}$ has 4 significant figures.
Significant Figures: Rules for Calculations
Rule 1 - Multiplication and Division: The result carries the same number of significant figures as the factor with the fewest significant figures.
Rule 2 - Addition and Subtraction: The result carries the same number of decimal places as the quantity with the fewest decimal places. Drawing a line next to the number with the fewest decimal places can help determine the number in the answer.
Examples of Precision: Preciseness can be indicated as 1/10, 1/100, etc.
Rules for Rounding
Rounding Guidelines:
Round down if the last significant digit dropped is 4 or less.
Round up if the last significant digit dropped is 5 or more.
Rounding Examples:
5.37 rounds to 5.4
5.34 rounds to 5.3
5.35 rounds to 5.4
5.349 rounds to 5.3
Important Note: Only the last significant digit being dropped dictates the rounding direction; all digits to the right are ignored.
Rounding in Multistep Calculations
Guideline: To avoid rounding errors, round only in the final answer, not intermediate steps.
Precaution: Keep track of significant figures by underlining the least significant digit in counted intermediate measurements.
Example Problem
Task: Report the result for the indicated arithmetic operations using the correct number of significant figures. Assume all values are measurements.
Solving Chemical Problems
Steps for Problem Solving
Write down what you want to know.
Start with the given measured quantity (identify what is given).
Apply conversion factors to cancel unwanted units.
Double-check: Does the answer make sense? Have units been remembered?
Dimensional Analysis
Unit Equation Definition: A statement of two equivalent quantities, such as $2.54 ext{ cm} = 1 ext{ in}$.
Conversion Factor Definition: A fractional quantity of a unit equation, with the units we are converting from on the bottom and the units we are converting to on the top.
Known Conversion Factors:
$1 ext{ in} = 2.54 ext{ cm}$ (exact)
$1 ext{ mL} = 1 ext{ cm}^{3} = 1 ext{ cc}$
$12 ext{ in} = 1 ext{ ft}$
$2.205 ext{ lb} = 1 ext{ kg}$ (4 significant figures)
$3 ext{ ft} = 1.0 ext{ yards}$
$1 ext{ L} = 1.057 ext{ qt}$
Density
Example Problem: The density of water at $25^{ ext{°C}}$ is $0.997 ext{ g/mL}$. A swimming pool holds 346 L of water; what is the mass of water in the pool?
Formula for Density:
where:\n - = Density\n - = Mass\n - = Volume
Important Note: Density can be used as a conversion factor. The density of ethanol is $0.789 ext{ g/mL}$. This can be expressed as two conversion factors:
and .
Touchscreen Technology
Indium Tin Oxide (ITO):
Example of a doped semiconductor.
Properties:
Highly conductive
Optically transparent
Easy to mass produce (cost-effective)
Brittle
Applications: Used in capacitive touchscreens.