Chapter 1
1.1 The Study of Chemistry
Experiments are the key to advancing our understanding of chemistry (or any science).
Scientific Method: A systematic approach to experimentation
• Observations: Natural phenomena and measured events; if universally consistent can be stated as a law
Hypothesis: Tentative explanation that explains observations (9vesS)
Experiment: Procedure to test hypothesis; measures on variable at a time Model (Theory): Set of conceptual assumptions that explains data from accumulated experiments; predicts related phenomena Further Experiment: Tests predictions based on model
1.1 The Study of Chemistry
Why is Chemistry called the central science?
• Knowledge of the principles of chemistry can facilitate understanding of other sciences
Chemistry: the study of matter and the changes that matter undergoes
Matter: anything that have mass and occupies space
All matter consists of various combinations of atoms.
The properties of matter depend on which elements it contains and how the atoms are arranged.
1.2 Classification of Matter
Chemists classify matter as either a substance or a mixture of substances
Substance a form of matter that has a specific composition and distinct properties; can either be elements or compounds
Every substance can exist as a solid, liquid, or gas
Condensed Phases: Solid and Liquid
Fluids: Liquids and Gases
Element: a substance that cannot be separated into simpler substances by chemical means (on the periodic table)
1.2 Classification of Matter
Compound: a substance composed of atoms of two or more elements chemically united in fixed proportions
Constituent Elements: the elements that make un a compound
• Constituent elements cannot be separated by any physical process and required a chemical reaction to be separated
1.3 Scientific Measurement
Quantitative Properties: properties that can be measured (expressed with numbers)
What is the other type of property? qualatative
Measurements are meaningless without units
International System of Units (SI Units): standard units used for measurements
Remember the base unit for mass is kilogram (kg) and the base unit for temperature is kelvin (k). Why do we use these?
How do we convert celsius to kelvin?
add 273
mass = kilograms
amount = mol
temp = kelvin
time = sec
length= meters
volume= liters
1.2 Classification of Matter
Mixture: a combination or two or more elements in which the substances retain their distinct identities
Mixtures can be solids, liquids, gases, or any combination of phases
Mixtures do not have a universal constant composition
Homogeneous Mixture; have uniform composition throughout (disolved locK)(aiir)
Heterogeneous Mixture: have variable composition; mixed substances remain distinct and discernible (hot disolved (sandwin rock
Mixtures can be separated by physical means without changing the identities of the components
1.3 Scientific Measurement
Derived Units: units "derived" through combining base units
Examples voline and insty
Important volume conversions to know: 1 L = 1 dm'3 1 mL = 1 cm'3
1.4 The Properties of Matter
Substances are identified by their properties and composition
Properties are either quantitative (measures and expressed with a number) or qualitative (not requiring explicit measurement).
Physical Property: a property that can be observed and measured without changing the identity of the substance
Example: melting/boiling points, color
Physical Change: a change in with the state of matter changes be the identity of matter does not
1.5 Uncertainty in Measurement
Chemistry makes use of two types of numbers: exact and inexact.
Exact Numbers: defined values or counted numbers
Inexact Numbers: measured values
We use SigFigs so we can indicate the uncertainty in values
Uncertain Digit: the last digit in a measured value
1.4 The properties of Matter
Chemical Property: a property of a substance that cannot be studied without converting the substance into some other substance
Chemical Change: a process in which one or more substances is changed into one or more new substances
Properties can either be extensive or intensive
Extensive Properties: depend on the amount of matter
Example: Mass
Intensive Properties: doe not depend on the amount of matter
Example: Density
1.6 Using Units and Solving Problems
Conversion Factor: a fraction in which the same quantity is expressed one way in the numerator and another way in the denominator (lin/2.54cm)
Conversion factors are equal to one so the fraction can always be used as the inverse
(lin/2.54cm = 2.54cm/lin)
Dimensional Analysis (Factor-Label Method): using conversion factors in problem solving (convert 3.2 ft into cm)
1.5 Uncertainty in Measurements
We use accuracy and precision to gauge the quality of a set of measured numbers.
Accuracy: how close measured values are to the true value
Precision: how close multiple measured values are to each other