General Chemistry: Core Concepts and Foundations

General Chemistry Overview

General Chemistry is the study of substances, their properties, and the transformations they undergo. This foundational science builds up from atomic and subatomic properties to the bulk properties of materials, providing essential knowledge for understanding the natural world and many applied sciences.

• Goals of General Chemistry:

  • Develop basic skills to understand chemistry fundamentals

  • Survey the major subfields of chemistry

  • Build knowledge from atomic structure to macroscopic properties

• Chemicals: All substances studied in chemistry, whether naturally occurring or synthetic.

Basic Concepts of Chemistry

Matter, Energy, and Measurement

Understanding chemistry begins with the study of matter, its forms, and how it is measured. Accurate measurement and classification are essential for scientific analysis.

• Matter: Anything that has mass and occupies space.

• Types of Matter:

  • Elements: Pure substances consisting of only one type of atom (e.g., Fe, Au, O2).

  • Compounds: Substances composed of two or more different elements chemically combined in fixed ratios (e.g., H2O, NaCl).

  • Mixtures: Physical combinations of two or more substances where each retains its own properties. Mixtures can be homogeneous (uniform composition, e.g., salt water) or heterogeneous (non-uniform, e.g., mud).

• Energy: The capacity to do work or transfer heat. Chemistry often studies how energy changes accompany chemical transformations.

• Measurement: Quantitative observations in chemistry require standardized units and careful attention to accuracy and precision.

Accuracy vs. Precision

• Accuracy: How close a measured value is to the true or accepted value.

• Precision: How close repeated measurements are to each other, regardless of their accuracy.

Atoms, Molecules, and Ions

Atoms are the fundamental units of matter, while molecules and ions represent combinations of atoms with distinct properties.

• Atoms: The smallest unit of an element that retains its chemical identity.

• Molecules: Groups of two or more atoms bonded together (e.g., H2O, O2).

• Ions: Atoms or molecules that have gained or lost electrons, resulting in a net charge (e.g., Na+, Cl-).

Classification and Properties of Matter

States of Matter

Matter exists in different physical states, each with unique characteristics.

• Solid: Definite shape and volume; particles are closely packed.

• Liquid: Definite volume but takes the shape of its container; particles are less tightly packed than in solids.

• Gas: No definite shape or volume; particles are far apart and move freely.

Properties of Matter

• Physical Properties: Can be observed without changing the substance's identity (e.g., color, melting point, density).

• Chemical Properties: Describe how a substance interacts with other substances (e.g., flammability, reactivity).

• Intensive Properties: Do not depend on the amount of substance (e.g., density, boiling point).

• Extensive Properties: Depend on the amount of substance (e.g., mass, volume).

Physical vs. Chemical Changes

• Physical Change: Alters the form or appearance but not the composition (e.g., melting, boiling).

• Chemical Change: Results in the formation of new substances (e.g., combustion, rusting).

Measurement in Chemistry

SI Units and Prefixes

Chemists use the International System of Units (SI) for consistency in measurements. Prefixes indicate multiples or fractions of base units.

Prefix	Symbol	Factor	Example
kilo	k	103	1 kilowatt (kW) = 1 × 103 W
centi	c	10-2	1 centimeter (cm) = 1 × 10-2 m
milli	m	10-3	1 milligram (mg) = 1 × 10-3 g
micro	μ	10-6	1 microliter (μL) = 1 × 10-6 L
nano	n	10-9	1 nanometer (nm) = 1 × 10-9 m

SI Base Units

Quantity	Name of Unit	Abbreviation
Mass	Kilogram	kg
Length	Meter	m
Time	Second	s
Temperature	Kelvin	K
Amount of substance	Mole	mol
Luminous intensity	Candela	cd

Significant Figures

Significant figures (sig figs) reflect the precision of a measured quantity. Proper use of significant figures is essential for reporting scientific data accurately.

• All non-zero digits are significant (e.g., 123.5 has 4 sig figs).

• Zeros between non-zero digits are significant (e.g., 2500.3 has 5 sig figs).

• Leading zeros are not significant (e.g., 0.02 has 1 sig fig).

• Trailing zeros are significant only if there is a decimal point (e.g., 0.0200 has 3 sig figs).

Significant Figures in Calculations

• Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

• Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

Example: Applying Significant Figures

• Adding 12.11 (2 decimal places) and 0.3 (1 decimal place):

  • Result: 12.4 (rounded to 1 decimal place)

• Multiplying 2.5 (2 sig figs) by 3.42 (3 sig figs):

  • Result: 8.6 (rounded to 2 sig figs)

Additional info:

• The notes reference the periodic table, which organizes elements by atomic number and properties.

• Polyatomic elements (e.g., O2, H2, S8) are elements that exist naturally as molecules containing more than one atom.

• Mixtures can be separated by physical means, such as filtration or evaporation.

• dimensional analysis