Basic Concepts in Chemistry

Matter: Anything that has mass and occupies space.
- States: Solid, Liquid, Gas, Plasma.
Atoms: Basic unit of matter, composed of protons, neutrons, and electrons.
- Protons (+), Neutrons (neutral), Electrons (−).
Elements: Pure substances that cannot be broken down.
- Represented by symbols (e.g., H for Hydrogen, O for Oxygen).
Compounds: Substances formed when two or more elements chemically bond.
- Example: Water (H₂O), Carbon Dioxide (CO₂).

Ionic Bonds: Formed by the transfer of electrons from one atom to another.
- Typically between metals and nonmetals.
Covalent Bonds: Formed by the sharing of electrons between atoms.
- Typically between nonmetals.
Metallic Bonds: Formed by the attraction between metal ions and delocalized electrons.

Types of Reactions:
- Synthesis: A + B → AB
- Decomposition: AB → A + B
- Single Replacement: A + BC → AC + B
- Double Replacement: AB + CD → AC + BD
- Combustion: Hydrocarbon + O₂ → CO₂ + H₂O
Balancing Reactions: Law of Conservation of Mass; the number of atoms must be equal on both sides.

Groups/Families: Vertical columns; elements share similar properties.
- Example: Group 1 (Alkali Metals), Group 17 (Halogens).
Periods: Horizontal rows; properties change progressively.
Metals, Nonmetals, and Metalloids:
- Metals: Good conductors, malleable.
- Nonmetals: Poor conductors, brittle.
- Metalloids: Properties of both metals and nonmetals.

Phase Changes:
- Melting, Freezing, Vaporization, Condensation, Sublimation, Deposition.
Properties:
- Physical: Observable without changing composition (e.g., color, melting point).
- Chemical: Relates to a substance's ability to undergo changes (e.g., reactivity).

Solution: Homogeneous mixture of solute and solvent.
- Solvent: Substance that dissolves the solute (e.g., water).
- Solute: Substance being dissolved (e.g., salt).
Types of Mixtures:
- Homogeneous: Uniform composition (e.g., air).
- Heterogeneous: Non-uniform composition (e.g., salad).

Acids: Substances that donate protons (H⁺) in a solution.
- Example: Hydrochloric acid (HCl).
Bases: Substances that accept protons or donate hydroxide ions (OH⁻).
- Example: Sodium hydroxide (NaOH).
pH Scale: Measures acidity/basicity.
- Scale: 0 (acidic) to 14 (basic), 7 is neutral.

Reaction Rate: Speed at which reactants turn into products.
- Influenced by concentration, temperature, surface area, and catalysts.
Chemical Equilibrium: State where the rate of forward reaction equals the rate of reverse reaction.
- Le Châtelier's Principle: System at equilibrium will adjust to counteract changes in conditions.

Matter has mass and occupies space; exists in solid, liquid, gas, and plasma states.
Atoms are the fundamental units of matter, containing protons (+), neutrons (neutral), and electrons (−).
Elements are pure substances that cannot be broken down, represented by symbols (e.g., H for Hydrogen, O for Oxygen).
Compounds form when two or more elements chemically bond, such as water (H₂O) and carbon dioxide (CO₂).

Ionic bonds form through electron transfer, commonly between metals and nonmetals.
Covalent bonds involve the sharing of electrons, typically occurring between nonmetals.
Metallic bonds result from the attraction between metal ions and delocalized electrons.

Types of reactions include:
- Synthesis (A + B → AB)
- Decomposition (AB → A + B)
- Single Replacement (A + BC → AC + B)
- Double Replacement (AB + CD → AC + BD)
- Combustion (Hydrocarbon + O₂ → CO₂ + H₂O)
Balancing reactions is essential to adhere to the law of conservation of mass, ensuring equal atom numbers on both sides.

Groups (vertical columns) indicate elements with similar properties, such as Group 1 (Alkali Metals) and Group 17 (Halogens).
Periods (horizontal rows) reflect progressive changes in properties across the table.
Metals are good conductors and malleable, nonmetals are poor conductors and brittle, and metalloids display characteristics of both.

Phase changes include melting, freezing, vaporization, condensation, sublimation, and deposition.
Physical properties can be observed without altering the substance, while chemical properties relate to a substance’s reactivity and potential changes.

A solution is a homogeneous mixture consisting of a solute (substance being dissolved) and a solvent (substance that dissolves the solute, e.g., water).
Mixtures can be homogeneous (uniform composition, e.g., air) or heterogeneous (non-uniform composition, e.g., salad).

Acids donate protons (H⁺) in a solution; hydrochloric acid (HCl) is an example.
Bases accept protons or provide hydroxide ions (OH⁻), such as sodium hydroxide (NaOH).
The pH scale ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

Endothermic reactions absorb energy (heat) from their surroundings.
Exothermic reactions release energy (heat).
Enthalpy (ΔH) measures heat content, while entropy (ΔS) gauges disorder or randomness in a system.

Reaction rate indicates how quickly reactants transform into products, influenced by concentration, temperature, surface area, and catalysts.
Chemical equilibrium occurs when the forward and reverse reaction rates are equal.
Le Châtelier's Principle states that a system at equilibrium will adjust to counteract any changes in conditions.