General Chemistry Fundamentals: Classification, Atomic Theory, Compounds, and Calculations

Classification of Matter

Properties of Matter

Matter can be described by its physical and chemical properties. These properties help in identifying and classifying substances.

• Density: Mass per unit volume of a substance.

• Color: Physical property observed visually.

• Combustibility: Chemical property describing the ability to burn.

• Melting Point: Temperature at which a solid becomes a liquid.

• Mass: Amount of matter in a substance.

Classification of Materials

Materials are classified as elements, compounds, homogeneous mixtures, or heterogeneous mixtures.

• Element: Pure substance consisting of one type of atom (e.g., Antimony).

• Compound: Substance formed from two or more elements chemically combined (e.g., Steel).

• Homogeneous Mixture: Uniform composition throughout (e.g., Apple juice).

• Heterogeneous Mixture: Non-uniform composition (e.g., Granite, Soil, Wood).

Example: A snow cone is a heterogeneous mixture, not a homogeneous mixture.

Units, Conversions, and Calculations

Density and Unit Conversion

Density is often converted between units for practical applications.

• Density of Iron (Fe): $7.86\ \text{g/mL}$

• Conversion: To convert to pounds per cubic foot, use:

  • $1\ \text{foot} = 30.48\ \text{cm}$

  • $1\ \text{lb} = 453.6\ \text{g}$

  • $1\ \text{mL} = 1\ \text{cm}^3$

Distance and Volume Units

• Ångström: $1\ \text{Å} = 1 \times 10^{-10}\ \text{m}$

• Volume: $1\ \text{in} = 2.54\ \text{cm}$

Gasoline Consumption Calculation

To calculate total cost of gasoline for a trip:

• Distance: 4500 miles

• Fuel Efficiency: 13 miles/gallon

• Price per Gallon: $1.27

• Calculation:

  • Gallons used: $\frac{4500}{13} \approx 346.15$ gallons

  • Total cost: $346.15 \times 1.27 \approx $439.61

Atomic Structure and Elements

Atomic Number, Mass Number, and Isotopes

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

• Mass Number (A): Sum of protons and neutrons.

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

Element Symbols and Incorrect Matches

• Cu: Copper

• Pb: Lead

• K: Potassium

• Cr: Chromium

• Bi: Bismuth

• Example: Incorrect match: K for potassium (should be correct; check for other mismatches).

Compounds and Chemical Formulas

Ionic and Molecular Compounds

• Ionic Compound: Formed from metals and nonmetals; consists of cations and anions (e.g., NaCl, CaO).

• Molecular Compound: Formed from nonmetals; consists of molecules (e.g., H2O, NH3).

Empirical and Molecular Formulas

• Empirical Formula: Simplest whole-number ratio of atoms in a compound.

• Molecular Formula: Actual number of atoms of each element in a molecule.

• Example: An alkene hydrocarbon with empirical formula CH and molar mass 26.0 amu has molecular formula C2H2.

Calculating Percent Composition

• Percent by Mass: $\%\ \text{element} = \frac{\text{mass of element in 1 mol of compound}}{\text{molar mass of compound}} \times 100$

• Example: % Oxygen in NaHCO3 (sodium bicarbonate)

Stoichiometry and Mole Concept

Mole and Avogadro's Number

• Mole: Amount of substance containing $6.022 \times 10^{23}$ particles (Avogadro's number).

• Example: 1 mole of H2O contains $6.022 \times 10^{23}$ molecules.

Calculating Number of Atoms/Molecules

• Number of Atoms: $\text{Number of atoms} = \frac{\text{mass}}{\text{molar mass}} \times \text{Avogadro's number}$

• Example: Number of hydrogen atoms in 27.0 g of H2O

Atomic Theory and Laws

Dalton's Atomic Theory

• Elements are composed of small indivisible particles called atoms.

• Atoms of the same element are identical in mass and properties.

• Atoms combine in simple whole-number ratios to form compounds.

• Atoms cannot be created or destroyed in chemical reactions.

Law of Definite Proportions

• A chemical compound always contains the same proportion of elements by mass.

• Example: Water is always 89% oxygen and 11% hydrogen by mass.

Tables

Classification of Compounds and Ions

Compound/Ion	Type
H2O	Molecular
Na2CO3	Ionic
NH4Cl	Ionic
CaO	Ionic
CO2	Molecular

Common Ions and Charges

Ion	Charge
Oxide	-2
Fluoride	-1
Hydroxide	-1
Nitrate	-1
Acetate	-1

Additional info:

• Some questions involve empirical and molecular formula calculations, percent composition, and stoichiometry, which are foundational for General Chemistry.

• Unit conversions and classification of matter are essential for understanding chemical properties and reactions.

• Atomic theory and chemical laws provide the theoretical basis for chemical behavior and composition.