Key Concepts in Chemistry

Key Concepts in Chemistry

• Matter

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

• Atoms

  • Basic unit of matter; consist of protons, neutrons, and electrons.
  • Atomic number = number of protons.
  • Mass number = protons + neutrons.

• Elements and Compounds

  • Element: pure substance made of one type of atom (e.g., O, H).
  • Compound: substance formed from two or more elements chemically bonded (e.g., H2O).

• Periodic Table

  • Organized chart of elements based on atomic number.
  • Groups: vertical columns (elements with similar properties).
  • Periods: horizontal rows (indicate the number of electron shells).

• Chemical Bonds

  • Ionic Bonds: electron transfer between atoms (e.g., NaCl).
  • Covalent Bonds: sharing of electron pairs between atoms (e.g., H2O).
  • Metallic Bonds: attraction between metal ions and delocalized electrons.

• Chemical Reactions

  • Process of transforming reactants into products.
  • 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

• Acids and Bases

  • Acids: substances that donate protons (H+) in solution (e.g., HCl).
  • Bases: substances that accept protons or donate hydroxide ions (OH−) (e.g., NaOH).
  • pH scale: measures the acidity or alkalinity of a solution (0-14; 7 is neutral).

• Stoichiometry

  • Relationship between reactants and products in a chemical reaction.
  • Uses mole ratios from balanced equations to calculate quantities.

• States of Matter

  • Solid: definite shape and volume, closely packed particles.
  • Liquid: definite volume, takes shape of container, less tightly packed than solids.
  • Gas: no definite shape or volume, particles are far apart and move freely.

• Thermochemistry

  • Study of heat changes during chemical reactions.
  • Endothermic: absorbs heat (ΔH > 0).
  • Exothermic: releases heat (ΔH < 0).

• Chemical Kinetics

  • Study of reaction rates and how they change under varying conditions.
  • Factors affecting reaction rates: concentration, temperature, surface area, catalysts.

• Chemical Equilibrium

  • State where the forward and reverse reactions occur at the same rate.
  • Dynamic equilibrium: concentrations of reactants and products remain constant, but reactions continue.

Important Laboratory Techniques

• Titration

  • Method for determining the concentration of an unknown solution by reacting it with a standard solution.

• Chromatography

  • Technique for separating mixtures based on different affinities of components to the stationary phase.

• Spectroscopy

  • Analyzing the interaction of light with matter to determine chemical composition.

• Filtration

  • Process of separating solids from liquids using a barrier (filter).

Safety in Chemistry

• Always wear appropriate personal protective equipment (PPE): gloves, goggles, lab coats.
• Understand Material Safety Data Sheets (MSDS) for chemicals used.
• Handle chemicals in well-ventilated areas or fume hoods.

Matter

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

Atoms

• The basic building blocks of matter.
• Consist of protons, neutrons, and electrons.
• Atomic number: number of protons in an atom's nucleus.
• Mass number: sum of protons and neutrons in an atom's nucleus.

Elements and Compounds

• Element: A pure substance composed of only one type of atom (e.g., oxygen, hydrogen).
• Compound: A substance formed from two or more elements chemically bonded together (e.g., water (H₂O)).

Periodic Table

• An organized chart of elements arranged by increasing atomic number.
• Groups: Vertical columns of elements with similar properties.
• Periods: Horizontal rows of elements with the same number of electron shells.

Chemical Bonds

• Ionic Bonds: formed by the transfer of electrons between atoms (e.g., sodium chloride (NaCl)).
• Covalent Bonds: formed by the sharing of electron pairs between atoms (e.g., water (H₂O)).
• Metallic Bonds: formed by the attraction between metal ions and delocalized electrons (e.g., copper (Cu)).

Chemical Reactions

• A process that involves the transformation of reactants into products.
• Types of chemical reactions:
  • Synthesis: A + B → AB (e.g., formation of water from hydrogen and oxygen).
  • Decomposition: AB → A + B (e.g., breaking down hydrogen peroxide into water and oxygen).
  • Single Replacement: A + BC → AC + B (e.g., reaction of zinc with hydrochloric acid).
  • Double Replacement: AB + CD → AD + CB (e.g., reaction of silver nitrate with sodium chloride).
  • Combustion: Hydrocarbon + O2 → CO2 + H2O (e.g., burning of fuels like wood).

Acids and Bases

• Acids: Substances that donate protons (H+) in solution (e.g., hydrochloric acid (HCl)).
• Bases: Substances that accept protons or donate hydroxide ions (OH-) in solution (e.g., sodium hydroxide (NaOH)).
• pH scale: Measures the acidity or alkalinity of a solution (0-14; 7 is neutral).

Stoichiometry

• The study of the quantitative relationships between reactants and products in chemical reactions.
• Uses mole ratios derived from balanced chemical equations to calculate quantities.

States of Matter

• Solid: Definite shape and volume, closely packed particles.
• Liquid: Definite volume, takes shape of its container, less tightly packed than solids.
• Gas: No definite shape or volume, particles are far apart and move freely.

Thermochemistry

• The study of heat changes during chemical reactions.
• Endothermic: Reactions that absorb heat (ΔH > 0).
• Exothermic: Reactions that release heat (ΔH < 0).

Chemical Kinetics

• The study of reaction rates and how they change under varying conditions.
• Factors affecting reaction rates:
  • Concentration of reactants
  • Temperature
  • Surface area of reactants
  • Presence of catalysts

Chemical Equilibrium

• A state where the rates of the forward and reverse reactions are equal.
• Dynamic equilibrium: Concentrations of reactants and products remain constant, but reactions continue.

Important Laboratory Techniques

• Titration: Determining the concentration of an unknown solution by reacting it with a standard solution.
• Chromatography: Separating mixtures based on different affinities of components to the stationary phase.
• Spectroscopy: Analyzing the interaction of light with matter to determine chemical composition.
• Filtration: Separating solids from liquids using a filter.

Safety in Chemistry

• Always wear appropriate Personal Protective Equipment (PPE): Gloves, goggles, lab coats.
• Understand Material Safety Data Sheets (MSDS) for chemicals used.
• Handle chemicals in well-ventilated areas or fume hoods.