"Your alarm goes off and, after hitting “snooze” once or twice, you pry yourself out of bed. You make a cup of coffee to help you get going, and then you shower, get dressed, eat breakfast, and check your phone for messages. On your way to school, you stop to fill your car’s gas tank, almost making you late for the first day of chemistry class. As you find a seat in the classroom, you read the question projected on the screen: “Welcome to class! Why should we study chemistry?”
Do you have an answer? You may be studying chemistry because it fulfills an academic requirement, but if you consider your daily activities, you might find chemistry interesting for other reasons. Most everything you do and encounter during your day involves chemistry. Making coffee, cooking eggs, and toasting bread involve chemistry. The products you use—like soap and shampoo, the fabrics you wear, the electronics that keep you connected to your world, the gasoline that propels your car—all of these and more involve chemical substances and processes. Whether you are aware or not, chemistry is part of your everyday world. In this course, you will learn many of the essential principles underlying the chemistry of modern-day life."
"
Chemistry deals with the composition, structure, and properties of matter, and the ways by which various forms of matter may be interconverted. Thus, it occupies a central place in the study and practice of science and technology. Chemists use the scientific method to perform experiments, pose hypotheses, and formulate laws and develop theories, so that they can better understand the behavior of the natural world. To do so, they operate in the macroscopic, microscopic, and symbolic domains. Chemists measure, analyze, purify, and synthesize a wide variety of substances that are important to our lives.
Matter is anything that occupies space and has mass. The basic building block of matter is the atom, the smallest unit of an element that can enter into combinations with atoms of the same or other elements. In many substances, atoms are combined into molecules. On earth, matter commonly exists in three states: solids, of fixed shape and volume; liquids, of variable shape but fixed volume; and gases, of variable shape and volume. Under high-temperature conditions, matter also can exist as a plasma. Most matter is a mixture: It is composed of two or more types of matter that can be present in varying amounts and can be separated by physical means. Heterogeneous mixtures vary in composition from point to point; homogeneous mixtures have the same composition from point to point. Pure substances consist of only one type of matter. A pure substance can be an element, which consists of only one type of atom and cannot be broken down by a chemical change, or a compound, which consists of two or more types of atoms.
All substances have distinct physical and chemical properties, and may undergo physical or chemical changes. Physical properties, such as hardness and boiling point, and physical changes, such as melting or freezing, do not involve a change in the composition of matter. Chemical properties, such flammability and acidity, and chemical changes, such as rusting, involve production of matter that differs from that present beforehand.
Measurable properties fall into one of two categories. Extensive properties depend on the amount of matter present, for example, the mass of gold. Intensive properties do not depend on the amount of matter present, for example, the density of gold. Heat is an example of an extensive property, and temperature is an example of an intensive property.
Measurements provide quantitative information that is critical in studying and practicing chemistry. Each measurement has an amount, a unit for comparison, and an uncertainty. Measurements can be represented in either decimal or scientific notation. Scientists primarily use SI (International System) units such as meters, seconds, and kilograms, as well as derived units, such as liters (for volume) and g/cm3 (for density). In many cases, it is convenient to use prefixes that yield fractional and multiple units, such as microseconds (10−6 seconds) and megahertz (106 hertz), respectively.
Quantities can be defined or measured. Measured quantities have an associated uncertainty that is represented by the number of significant figures in the quantity’s number. The uncertainty of a calculated quantity depends on the uncertainties in the quantities used in the calculation and is reflected in how the value is rounded. Quantities are characterized with regard to accuracy (closeness to a true or accepted value) and precision (variation among replicate measurement results).
Measurements are made using a variety of units. It is often useful or necessary to convert a measured quantity from one unit into another. These conversions are accomplished using unit conversion factors, which are derived by simple applications of a mathematical approach called the factor-label method or dimensional analysis. This strategy is also employed to calculate sought quantities using measured quantities and appropriate mathematical relations.
"
accuracy
how closely a measurement aligns with a correct value
atom
smallest particle of an element that can enter into a chemical combination
Celsius (°C)
unit of temperature; water freezes at 0 °C and boils at 100 °C on this scale
chemical change
change producing a different kind of matter from the original kind of matter
chemical property
behavior that is related to the change of one kind of matter into another kind of matter
chemistry
study of the composition, properties, and interactions of matter
compound
pure substance that can be decomposed into two or more elements
cubic centimeter (cm3 or cc)
volume of a cube with an edge length of exactly 1 cm
cubic meter (m3)
SI unit of volume
density
ratio of mass to volume for a substance or object
dimensional analysis
(also, factor-label method) versatile mathematical approach that can be applied to computations ranging from simple unit conversions to more complex, multi-step calculations involving several different quantities
element
substance that is composed of a single type of atom; a substance that cannot be decomposed by a chemical change
exact number
number derived by counting or by definition
extensive property
property of a substance that depends on the amount of the substance
Fahrenheit
unit of temperature; water freezes at 32 °F and boils at 212 °F on this scale
gas
state in which matter has neither definite volume nor shape
heterogeneous mixture
combination of substances with a composition that varies from point to point
homogeneous mixture
(also, solution) combination of substances with a composition that is uniform throughout
hypothesis
tentative explanation of observations that acts as a guide for gathering and checking information
intensive property
property of a substance that is independent of the amount of the substance
kelvin (K)
SI unit of temperature; 273.15 K = 0 ºC
kilogram (kg)
standard SI unit of mass
law
statement that summarizes a vast number of experimental observations, and describes or predicts some aspect of the natural world
law of conservation of matter
when matter converts from one type to another or changes form, there is no detectable change in the total amount of matter present
length
measure of one dimension of an object
liquid
state of matter that has a definite volume but indefinite shape
liter (L)
(also, cubic decimeter) unit of volume; 1 L = 1,000 cm3
macroscopic domain
realm of everyday things that are large enough to sense directly by human sight and touch
mass
fundamental property indicating amount of matter
matter
anything that occupies space and has mass
meter (m)
standard metric and SI unit of length; 1 m = approximately 1.094 yards
microscopic domain
realm of things that are much too small to be sensed directly
milliliter (mL)
1/1,000 of a liter; equal to 1 cm3
mixture
matter that can be separated into its components by physical means
molecule
bonded collection of two or more atoms of the same or different elements
physical change
change in the state or properties of matter that does not involve a change in its chemical composition
physical property
characteristic of matter that is not associated with any change in its chemical composition
plasma
gaseous state of matter containing a large number of electrically charged atoms and/or molecules
precision
how closely a measurement matches the same measurement when repeated
pure substance
homogeneous substance that has a constant composition
rounding
procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation
scientific method
path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory
second (s)
SI unit of time
SI units (International System of Units)
standards fixed by international agreement in the International System of Units (Le Système International d’Unités)
significant figures
(also, significant digits) all of the measured digits in a determination, including the uncertain last digit
solid
state of matter that is rigid, has a definite shape, and has a fairly constant volume
symbolic domain
specialized language used to represent components of the macroscopic and microscopic domains, such as chemical symbols, chemical formulas, chemical equations, graphs, drawings, and calculations
temperature
intensive property representing the hotness or coldness of matter
theory
well-substantiated, comprehensive, testable explanation of a particular aspect of nature
uncertainty
estimate of amount by which measurement differs from true value
unit
standard of comparison for measurements
unit conversion factor
ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit
volume
amount of space occupied by an object
weight
force that gravity exerts on an object