Key Concepts in Chemistry

Matter: Anything that has mass and occupies space.
Atoms: The basic units of matter; consist of protons, neutrons, and electrons.
Elements: Pure substances made of only one type of atom; represented on the periodic table.
Compounds: Substances formed from two or more elements that are chemically bonded.

Ionic Bonds: Formed when electrons are transferred from one atom to another, creating ions.
Covalent Bonds: Formed when atoms share electrons.
Metallic Bonds: Involves the pooling of electrons among a lattice of metal atoms.

Solid: Defined shape and volume; particles are closely packed.
Liquid: Defined volume but takes the shape of its container; particles are less tightly packed.
Gas: No defined shape or volume; particles are far apart and move freely.

Reactants: Substances that undergo a change in a chemical reaction.
Products: Substances formed as a result of a chemical reaction.
Types of Reactions:
- Synthesis: Two or more substances combine to form a new compound.
- Decomposition: A compound breaks down into simpler substances.
- Single Replacement: One element replaces another in a compound.
- Double Replacement: Exchange of ions between two compounds.
- Combustion: Reaction with oxygen producing heat and light.

Mole Concept: A mole is 6.022 x 10²³ particles (atoms, molecules).
Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol).

Solvent: The substance in which a solute is dissolved (usually a liquid).
Solute: The substance that is dissolved.
Concentration: Amount of solute per unit volume of solution; commonly expressed in molarity (M).

Acids: Substances that donate protons (H⁺ ions) in solution; have a pH less than 7.
Bases: Substances that accept protons or donate hydroxide ions (OH⁻); have a pH greater than 7.
pH Scale: Measures the acidity or basicity of a solution, ranging from 0 (strong acid) to 14 (strong base).

First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.
Enthalpy (H): Total heat content of a system, used to quantify energy changes in reactions.
Entropy (S): Measure of disorder or randomness in a system; tends to increase in spontaneous processes.

Reaction Rate: Speed at which reactants are converted into products; affected by concentration, temperature, and catalysts.
Chemical Equilibrium: State where the forward and reverse reactions occur at the same rate; concentrations of reactants and products remain constant.

Groups: Vertical columns; elements in the same group have similar chemical properties.
Periods: Horizontal rows; properties change progressively across a period.
Trends:
- Electronegativity: Tendency of an atom to attract electrons; increases across a period and decreases down a group.
- Atomic Radius: Size of an atom; decreases across a period and increases down a group.

Hydrocarbons: Compounds composed of hydrogen and carbon; can be aliphatic (chains) or aromatic (rings).
Functional Groups: Specific groups of atoms within molecules that determine the characteristics and chemical reactivity.

By understanding these key concepts, students can build a solid foundation in chemistry.

Matter includes anything with mass and volume.
Atoms are fundamental units of matter composed of protons, neutrons, and electrons.
Elements consist of only one type of atom and are listed in the periodic table.
Compounds are formed through chemical bonding between two or more different elements.

Ionic bonds involve the transfer of electrons between atoms, leading to the formation of charged ions.
Covalent bonds are characterized by the sharing of electrons between atoms.
Metallic bonds allow electrons to flow freely among a lattice of metal atoms.

Solids maintain a distinct shape and volume due to tightly packed particles.
Liquids have a defined volume but adapt to the shape of their container, with more spaced-out particles compared to solids.
Gases do not have a fixed shape or volume, as particles are widely spaced and move independently.

Reactants are substances that participate in chemical changes.
Products are the results of chemical reactions.
Synthesis occurs when multiple substances combine to form a new compound.
Decomposition involves breaking down a compound into simpler substances.
Single Replacement reactions feature one element substituting another within a compound.
Double Replacement reactions involve the exchange of ions between two compounds.
Combustion reactions consume oxygen and release heat and light.

A mole equals 6.022 x 10²³ individual particles, such as atoms or molecules.
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).

Solvents are materials in which solutes dissolve, typically liquids.
Solutes are the substances that dissolve within solvents.
Concentration indicates the amount of solute in a specified volume of solution, often measured in molarity (M).

Acids donate protons (H⁺ ions) in aqueous solutions and possess a pH below 7.
Bases accept protons or release hydroxide ions (OH⁻) in solution, with a pH above 7.
The pH scale spans from 0 (strong acids) to 14 (strong bases), quantifying the acidity or basicity of solutions.

The First Law of Thermodynamics states that energy is conserved and can only be transformed, not created or destroyed.
Enthalpy (H) reflects the total heat content of a system and is crucial for understanding energy changes in reactions.
Entropy (S) quantifies system disorder, generally increasing in spontaneous processes.

Reaction rates measure how quickly reactants convert to products, influenced by concentration, temperature, and catalysts.
Chemical equilibrium occurs when the forward and reverse reactions happen at equivalent rates, stabilizing concentrations of reactants and products.

Groups are vertical columns identifying elements with similar chemical properties.
Periods are horizontal rows exhibiting progressive changes in properties.
Electronegativity indicates an atom's ability to attract electrons, increasing across a period and decreasing down a group.
Atomic radius defines atom size, decreasing across a period and increasing down a group.

Hydrocarbons consist of only carbon and hydrogen, categorized into aliphatic (open chains) and aromatic (ring structures).
Functional groups influence a molecule's characteristics and reactivity, playing a critical role in organic compound behavior.