General Chemistry HOSA

⚛ Describe Chemistry Concepts, Measurements, & Calculations

Moles, Molar Mass, Energy — 20%

Core Concepts

• Matter → Anything that has mass and takes up space

• Law of Conservation of Mass → Matter is neither created nor destroyed

• Energy → Ability to do work or cause change

Measurements

• SI units

  • Mass → gram (g)

  • Volume → liter (L)

  • Temperature → Kelvin (K)

• Density formula

Density=massvolume\text{Density} = \frac{\text{mass}}{\text{volume}}Density=volumemass​

Mole Concept

• Mole (mol) → 6.022×10236.022 \times 10^{23}6.022×1023 particles

• Molar mass → Mass of 1 mole of a substance (g/mol)

• Conversions

  • grams ↔ moles ↔ particles

Energy

• Endothermic reaction → Absorbs energy

• Exothermic reaction → Releases energy

🧪 Identify Elements, Atoms, Ions, & Periodicity — 10%

Atomic Structure

• Proton → Positive charge, nucleus

• Neutron → No charge, nucleus

• Electron → Negative charge, electron cloud

Ions

• Cation → Positive ion (lost electrons)

• Anion → Negative ion (gained electrons)

Periodic Trends

• Atomic radius

  • Increases down a group

  • Decreases across a period

• Electronegativity

  • Increases across a period

  • Decreases down a group

🔥 Describe Chemical Reactions, Energy, & Solutions — 30%

Types of Reactions

• Synthesis → A + B → AB

• Decomposition → AB → A + B

• Single replacement → A + BC → AC + B

• Double replacement → AB + CD → AD + CB

• Combustion → Hydrocarbon + O₂ → CO₂ + H₂O

Reaction Rates

• Increased by:

  • Higher temperature

  • Higher concentration

  • Catalysts

  • Greater surface area

Solutions

• Solute → Substance being dissolved

• Solvent → Substance doing the dissolving

• Concentration → Amount of solute in solution

• Molarity

M=moles soluteliters solutionM = \frac{\text{moles solute}}{\text{liters solution}}M=liters solutionmoles solute​

⚖ Chemical Composition, Quantities, Kinetics, & Equilibrium — 10%

Stoichiometry

• Uses balanced equations to calculate quantities

• Limiting reactant → Reactant that runs out first

Kinetics

• Study of reaction rates

• Influenced by temperature, concentration, catalysts

Equilibrium

• Forward rate = reverse rate

• Le Châtelier’s Principle

  • System shifts to reduce stress

🔗 Bonding Concepts — 4%

Types of Bonds

• Ionic bond → Electron transfer (metal + nonmetal)

• Covalent bond → Electron sharing (nonmetals)

• Hydrogen bond → Weak attraction involving H

Polarity

• Polar bond → Unequal electron sharing

• Nonpolar bond → Equal sharing

⚛ Modern Atomic Theory — 4%

• Dalton → Atoms are indivisible (historical)

• Thomson → Electron discovered

• Rutherford → Dense nucleus

• Bohr → Energy levels

• Quantum Mechanical Model → Electron probability clouds

🧴 Acids vs Bases — 4%

Acids

• Produce H⁺ ions

• pH < 7

• Sour taste

Bases

• Produce OH⁻ ions

• pH > 7

• Bitter/slippery

pH Scale

• 0–6 → Acidic

• 7 → Neutral

• 8–14 → Basic

🧾 Chemical Nomenclature — 4%

Ionic Compounds

• Cation name + anion name

• Example: NaCl → sodium chloride

Covalent Compounds

• Use prefixes:

  • mono-, di-, tri-, tetra-, penta-

Acids

• -ide → hydro-___-ic acid

• -ate → ___-ic acid

• -ite → ___-ous acid

🧊 Properties of Matter — 10%

Physical Properties

• Mass, volume, density, melting point

Chemical Properties

• Reactivity, flammability

States of Matter

• Solid → Fixed shape & volume

• Liquid → Fixed volume, variable shape

• Gas → Variable shape & volume

⚡ Electrochemistry & Entropy — 4%

Electrochemistry

• Oxidation → Loss of electrons

• Reduction → Gain of electrons

• Redox reactions → Both occur together

Entropy

• Measure of disorder

• Higher entropy → More randomness