Fundamental Concepts in General Chemistry: Matter, Measurement, and Nomenclature

Matter and Properties of Substances

Physical and Chemical Properties and Changes

Understanding the nature of matter is foundational in chemistry. Matter can undergo physical or chemical changes, and its properties can be classified accordingly.

• Physical Properties: Characteristics that can be observed or measured without changing the substance's identity (e.g., melting point, boiling point, density).

• Chemical Properties: Characteristics that describe a substance's ability to undergo chemical changes (e.g., flammability, reactivity).

• Physical Change: A change that does not alter the chemical composition (e.g., phase changes like melting or boiling).

• Chemical Change: A process that results in the formation of new substances (e.g., rusting of iron).

General Properties of Gases, Liquids, and Solids:

• Gases: No fixed shape or volume, compressible, particles far apart.

• Liquids: Fixed volume, no fixed shape, incompressible, particles closer than in gases.

• Solids: Fixed shape and volume, incompressible, particles in fixed positions.

Classification of Matter:

• Pure Substances: Elements and compounds with uniform composition.

• Mixtures: Physical combinations of two or more substances; can be homogeneous (uniform, e.g., saltwater) or heterogeneous (non-uniform, e.g., salad).

Extensive vs. Intensive Properties:

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

• Intensive Properties: Independent of the amount of matter (e.g., density, boiling point).

Dimensional Analysis (Unit Conversion) & Significant Figures

Units, Prefixes, and Measurement

Accurate measurement and unit conversion are essential skills in chemistry.

• SI Units: Standard units for scientific measurement (e.g., meter, kilogram, second, mole).

• Prefix Multipliers: Used to express multiples or fractions of units (e.g., kilo-, milli-, micro-).

Significant Figures:

• Digits in a measurement that are known with certainty plus one estimated digit.

• Rules for determining significant figures include handling of zeros and decimal points.

• When performing calculations, the result should be reported with the correct number of significant figures.

Dimensional Analysis:

• Method for converting between units using conversion factors.

• Set up calculations so that units cancel appropriately, leaving the desired unit.

Density Calculations:

• Density is defined as mass per unit volume.

$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

Atom/Ion Symbolism & Nomenclature

Names and Symbols of Elements, Polyatomic Ions, and Naming Compounds

Chemists use a standardized system for naming elements, ions, and compounds. Mastery of these conventions is crucial for communication and problem-solving in chemistry.

• Elements: Each element has a unique symbol (e.g., H for hydrogen, O for oxygen). Elements are organized in the periodic table by atomic number.

• Groups: Columns in the periodic table (e.g., 1A, 2A, 7A, 8A) share similar chemical properties.

• Atomic Number (Z): Number of protons in the nucleus of an atom.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Ions: Atoms or molecules that have gained or lost electrons, resulting in a net charge.

Isotope Notation: Isotopes are represented as:

• $^{A}_{Z}\text{X}$, where A = mass number (protons + neutrons), Z = atomic number, X = element symbol.

Calculating Atomic Mass:

• Atomic mass is the weighted average of the masses of all naturally occurring isotopes of an element.

$\text{Atomic mass or atomic weight} = \sum \left[(\text{Isotope mass}) \times (\text{Fractional isotope abundance})\right]$

Elements to Memorize (Name and Symbol)

Students are expected to know the names and symbols of the following elements:

• H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Ag, Cd, Sn, I, Xe, Cs, Ba, Au, Hg, Pb, Rn

Ions with Predictable Charges and the Periodic Table

Certain groups in the periodic table form ions with predictable charges. The following table summarizes these ions:

Group	Common Ion(s)	Charge
1A	H+, Li+, Na+, K+, Rb+, Cs+	+1
2A	Mg2+, Ca2+, Sr2+, Ba2+	+2
3A	Al3+	+3
5A	N3-, P3-	-3
6A	O2-, S2-, Se2-, Te2-	-2
7A	F-, Cl-, Br-, I-	-1
8A	Noble Gases	0

Common Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded, carrying a net charge. The following table lists common polyatomic ions you are expected to know:

Formula	Name	Charge
NH4+	Ammonium	+1
OH-	Hydroxide	-1
NO3-	Nitrate	-1
NO2-	Nitrite	-1
ClO4-	Perchlorate	-1
ClO3-	Chlorate	-1
ClO2-	Chlorite	-1
ClO-	Hypochlorite	-1
CN-	Cyanide	-1
SCN-	Thiocyanate	-1
MnO4-	Permanaganate	-1
CH3COO-	Acetate	-1
HCO3-	Hydrogen carbonate (bicarbonate)	-1
HSO4-	Hydrogen sulfate	-1
SO32-	-2
SO42-	Sulfate	-2
S2O32-	Thiosulfate	-2
CO32-	Carbonate	-2
C2O42-	Oxalate	-2
CrO42-	Chromate	-2
Cr2O72-	Dichromate	-2
HPO42-	Hydrogen phosphate (monohydrogen phosphate)	-2
PO43-	Phosphate	-3

Atom-Mole-Mass Conversion

Conversions Between Grams, Moles, and Atoms

Stoichiometric calculations often require converting between mass, moles, and number of particles.

• Mole: The amount of substance containing Avogadro's number ($6.022 \times 10^{23}$) of entities (atoms, molecules, ions).

• Molar Mass: The mass of one mole of a substance, usually expressed in grams per mole (g/mol).

Key Conversion Relationships:

• Mass (g) ↔ Moles (mol): $\text{Moles} = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}}$

• Moles (mol) ↔ Number of Particles: $\text{Number of particles} = \text{Moles} \times 6.022 \times 10^{23}$

Formula Mass (Molar Mass) Calculation

Calculating the Mass of a Compound

The formula mass (or molar mass) of a compound is the sum of the atomic masses of all atoms in its chemical formula.

• For molecular compounds, add the atomic masses of each atom in the molecule.

• For ionic compounds, add the atomic masses of the ions in the empirical formula.

$\text{Molar mass} = \sum (\text{number of atoms of element} \times \text{atomic mass of element})$

Example: The molar mass of H2O is $2 \times 1.008$ (H) $+ 16.00$ (O) $= 18.02$ g/mol.

Additional info: Mastery of these foundational concepts is essential for success in subsequent chemistry topics, including chemical reactions, stoichiometry, and solution chemistry.