Basic Concepts of Chemistry

Basic Concepts of Chemistry

• Matter

  • Anything that has mass and occupies space.
  • Exists in states: solid, liquid, gas, and plasma.

• Atoms

  • Basic unit of matter.
  • Composed of protons (positive), neutrons (neutral), and electrons (negative).
  • Element: a substance made of one type of atom.

• Molecules

  • Two or more atoms bonded together.
  • Can be the same type of atoms (e.g., O₂) or different (e.g., H₂O).

Chemical Bonds

• Ionic Bonds

  • Formed through the transfer of electrons.
  • Typically between metals and nonmetals.

• Covalent Bonds

  • Formed by sharing electrons between atoms.
  • Common in nonmetals.

• Metallic Bonds

  • Involves the pooling of electrons in metals.
  • Allows for conductivity and malleability.

Chemical Reactions

• 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

• Law of Conservation of Mass

  • Mass is neither created nor destroyed in a chemical reaction.

The Periodic Table

• Organization

  • Elements arranged by increasing atomic number.
  • Groups (columns) share similar chemical properties.
  • Periods (rows) show trends in properties across a series.

• Key Groups

  • Alkali Metals (Group 1)
  • Alkaline Earth Metals (Group 2)
  • Transition Metals (Groups 3-12)
  • Halogens (Group 17)
  • Noble Gases (Group 18)

Acids and Bases

• Acids

  • Sour taste, pH less than 7.
  • Produce H⁺ ions in solution.
  • Examples: HCl, H₂SO₄.

• Bases

  • Bitter taste, slippery feel, pH greater than 7.
  • Produce OH⁻ ions in solution.
  • Examples: NaOH, KOH.

• pH Scale

  • Measures acidity or alkalinity from 0 to 14.
  • 7 is neutral; below 7 is acidic; above 7 is basic.

Stoichiometry

• Mole Concept

  • 1 mole = 6.022 x 10²³ particles (Avogadro's number).
  • Molar mass: mass of one mole of a substance (g/mol).

• Calculating Reactions

  • Use balanced equations to relate moles of reactants and products.

Thermochemistry

• Energy Changes

  • Exothermic reactions release energy (e.g., combustion).
  • Endothermic reactions absorb energy (e.g., photosynthesis).

• Enthalpy (ΔH)

  • Measure of total heat content in a system during a reaction.

Kinetics and Equilibrium

• Reaction Rate

  • Speed at which reactants are converted to products.
  • Influenced by concentration, temperature, surface area, and catalysts.

• Dynamic Equilibrium

  • Rate of forward reaction equals rate of reverse reaction in a closed system.
  • Concentrations of reactants and products remain constant.

Organic Chemistry

• Hydrocarbons

  • Compounds made of carbon and hydrogen.
  • Types: alkanes (single bonds), alkenes (double bonds), alkynes (triple bonds).

• Functional Groups

  • Specific groups of atoms that determine the characteristics of organic compounds.
  • Examples: hydroxyl (-OH), carboxyl (-COOH), amine (-NH₂).

These notes provide a foundation in key chemistry concepts and principles for further study or review.

Basic Concepts of Chemistry

• Matter is anything with mass and volume, existing in four states: solid, liquid, gas, and plasma.
• Atoms are the fundamental units of matter, consisting of protons (positively charged), neutrons (neutral), and electrons (negatively charged).
• An element is defined as a substance made up of only one type of atom.
• Molecules consist of two or more atoms bonded together and can be homonuclear (e.g., O₂) or heteronuclear (e.g., H₂O).

Chemical Bonds

• Ionic bonds involve the transfer of electrons and typically occur between metals and nonmetals.
• Covalent bonds are formed by the sharing of electrons, common among nonmetals.
• Metallic bonds result from the delocalization of electrons within metals, enabling conductivity and malleability.

Chemical Reactions

• Chemical reactions can be classified into several types:
  • 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)
• The Law of Conservation of Mass states that mass is conserved in a chemical reaction; it is neither created nor destroyed.

The Periodic Table

• The periodic table organizes elements by increasing atomic number, with vertical columns (groups) indicating similar chemical properties and horizontal rows (periods) showing trends in properties.
• Key element groups:
  • Alkali Metals (Group 1)
  • Alkaline Earth Metals (Group 2)
  • Transition Metals (Groups 3-12)
  • Halogens (Group 17)
  • Noble Gases (Group 18)

Acids and Bases

• Acids typically have a sour taste, a pH below 7, and release H⁺ ions in solutions; examples include HCl and H₂SO₄.
• Bases are characterized by a bitter taste, slippery feel, a pH above 7, and produce OH⁻ ions in solutions; common examples are NaOH and KOH.
• The pH scale ranges from 0 to 14, where 7 is neutral, below 7 indicates acidity, and above 7 indicates basicity.

Stoichiometry

• The mole concept states that one mole equals 6.022 x 10²³ particles (Avogadro's number), with molar mass being the mass of one mole of a substance expressed in grams per mole (g/mol).
• Balanced chemical equations are used to determine the relationships between moles of reactants and products in reactions.

Thermochemistry

• Energy changes during chemical reactions can be classified as:
  • Exothermic (release energy, e.g., combustion)
  • Endothermic (absorb energy, e.g., photosynthesis)
• Enthalpy (ΔH) is a measure of the total heat content of a system during a reaction.

Kinetics and Equilibrium

• The reaction rate refers to the speed at which reactants convert to products, influenced by factors such as concentration, temperature, surface area, and the presence of catalysts.
• Dynamic equilibrium is established when the rate of the forward reaction equals the rate of the reverse reaction in a closed system, keeping the concentrations of reactants and products constant.

Organic Chemistry

• Hydrocarbons are organic compounds composed solely of carbon and hydrogen, categorized into:
  • Alkanes (single bonds)
  • Alkenes (double bonds)
  • Alkynes (triple bonds)
• Functional groups are specific atom groups within organic compounds that determine their chemical properties, such as hydroxyl (-OH), carboxyl (-COOH), and amine (-NH₂).