Basic Concepts of Chemistry

Atoms: Basic units of matter; consist of protons, neutrons, and electrons.
Molecules: Two or more atoms bonded together.
Elements: Pure substances made of only one type of atom; represented on the periodic table (e.g., hydrogen, oxygen).

States of Matter

Solid: Definite shape and volume; particles are closely packed.
Liquid: Definite volume but takes the shape of the container; particles are close but can move past one another.
Gas: Neither definite shape nor volume; particles are far apart and move freely.
Plasma: Ionized gas with free-moving charged particles, found in stars and lightning.

Chemical Bonds

Ionic Bonds: Formed between metals and nonmetals where electrons are transferred.
Covalent Bonds: Formed when two nonmetals share electrons.
Metallic Bonds: Attraction between metal atoms and their shared electrons; allows conductivity and malleability.

Chemical Reactions

Reactants: Substances that undergo change in a chemical reaction.
Products: New substances formed as a result of a chemical reaction.
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 increase the concentration of hydrogen ions (H⁺) in solution (e.g., HCl, H₂SO₄).
Bases: Substances that increase hydroxide ions (OH⁻) in solution (e.g., NaOH, KOH).
pH Scale: Measures acidity or basicity; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

The Periodic Table

Elements organized by increasing atomic number.
Groups: Vertical columns; elements in a group have similar chemical properties.
Periods: Horizontal rows; properties change gradually across a period.
Key Groups:
- Alkali Metals: Group 1 (e.g., Li, Na)
- Alkaline Earth Metals: Group 2 (e.g., Mg, Ca)
- Transition Metals: Groups 3-12 (e.g., Fe, Cu)
- Halogens: Group 17 (e.g., F, Cl)
- Noble Gases: Group 18 (e.g., He, Ne)

Stoichiometry

Mole Concept: A mole is 6.022 × 10²³ particles (Avogadro's number).
Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol).
Balancing Equations: Necessary to ensure the law of conservation of mass is upheld; same number of atoms on both sides of the equation.

Thermodynamics

Endothermic Reactions: Absorb heat (temperature decreases).
Exothermic Reactions: Release heat (temperature increases).
Gibbs Free Energy (ΔG): Indicates spontaneity of a reaction; ΔG < 0 means the reaction is spontaneous.

Common Laboratory Techniques

Titration: Method used to determine the concentration of a solution by reacting it with a solution of known concentration.
Filtration: Separating solids from liquids using a filter.
Distillation: Purifying liquids based on differences in boiling points.
Crystallization: Method for separating solids from solutions; forms pure solid crystals.

Key Chemical Laws

Law of Conservation of Mass: In a closed system, mass is conserved in chemical reactions.
Law of Definite Proportions: A chemical compound always contains its component elements in fixed ratio by mass.
Ideal Gas Law: PV = nRT; relates pressure (P), volume (V), number of moles (n), the gas constant (R), and temperature (T).

These notes provide essential concepts and terminology within the field of chemistry, facilitating further study and understanding of the subject.

Basic Chemistry Concepts

Atoms: The fundamental building blocks of matter, composed of protons, neutrons, and electrons.
Molecules: Formed when two or more atoms bond together, creating new substances.
Elements: Pure substances composed of only one type of atom. They are organized on the Periodic Table (e.g., hydrogen, oxygen).

States of Matter

Solids: Have a definite shape and volume due to tightly packed particles.
Liquids: Maintains a definite volume but conforms to the shape of its container, with particles close together but able to move.
Gases: Lack a definite shape or volume, with particles far apart and free-moving.
Plasma: Ionized gas with free-moving charged particles, present in stars and lightning.

Chemical Bonds

Ionic Bonds: Form when electrons are transferred between metals and nonmetals, resulting in the formation of ions.
Covalent Bonds: Form when two nonmetals share electrons, creating molecules.
Metallic Bonds: Result from the attraction between metal atoms and their shared electrons, contributing to their conductivity and malleability.

Chemical Reactions

Reactants: Substances that change during a chemical reaction.
Products: New substances formed as a result of a chemical reaction.
Types of Reactions:
- Synthesis: Two or more reactants combine to form a single product (A + B → AB).
- Decomposition: A single reactant breaks down into two or more products (AB → A + B).
- Single Replacement: One element replaces another in a compound (A + BC → AC + B).
- Double Replacement: Elements in two compounds switch places (AB + CD → AD + CB).
- Combustion: A rapid reaction involving a fuel and an oxidant, usually oxygen, producing heat and light (Hydrocarbon + O₂ → CO₂ + H₂O).

Acids and Bases

Acids: Substances that increase the concentration of hydrogen ions (H⁺) in solution, making the solution acidic. Examples include hydrochloric acid (HCl) and sulfuric acid (H₂SO₄).
Bases: Substances that increase the concentration of hydroxide ions (OH⁻) in solution, making the solution basic or alkaline. Examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
pH Scale: A measure of acidity or basicity ranging from 0 (most acidic) to 14 (most basic), with 7 representing neutral.

The Periodic Table

Organization: Elements are arranged in order of increasing atomic number.
Groups: Vertical columns of elements with similar chemical properties.
Periods: Horizontal rows of elements with gradually changing properties across the period.
Key Groups:
- Alkali Metals: Group 1 (e.g., lithium (Li), sodium (Na) - highly reactive).
- Alkaline Earth Metals: Group 2 (e.g., magnesium (Mg), calcium (Ca) - reactive).
- Transition Metals: Groups 3-12 (e.g., iron (Fe), copper (Cu) - often form colored compounds).
- Halogens: Group 17 (e.g., fluorine (F), chlorine (Cl) - very reactive nonmetals).
- Noble Gases: Group 18 (e.g., helium (He), neon (Ne) - unreactive gases).

Stoichiometry

Mole Concept: 1 mole of a substance contains 6.022 × 10²³ particles (Avogadro's number).
Molar Mass: The mass of one mole of a substance, measured in grams per mole (g/mol).
Balancing Equations: Ensures the law of conservation of mass is upheld by having the same number of atoms of each element on both sides of the equation.

Thermodynamics

Endothermic Reactions: Absorb heat from the surroundings, causing a decrease in temperature.
Exothermic Reactions: Release heat into the surroundings, causing an increase in temperature.
Gibbs Free Energy (ΔG): Determines the spontaneity of a reaction. A negative ΔG indicates a spontaneous reaction.

Common Laboratory Techniques

Titration: Used to determine the concentration of a solution by reacting it with a solution of known concentration.
Filtration: Separates solids from liquids using a filter.
Distillation: Purifies liquids based on differences in their boiling points.
Crystallization: Separates solids from solutions by forming pure solid crystals.

Key Chemical Laws

Law of Conservation of Mass: In a closed system, the total mass remains constant during a chemical reaction. Mass is neither created nor destroyed.
Law of Definite Proportions: A chemical compound always contains the same elements in the same proportions by mass.
Ideal Gas Law: Relates pressure (P), volume (V), number of moles (n), the gas constant (R), and temperature (T) of an ideal gas: PV = nRT.