Chem

Matter

Anything that has mass and occupies space.

Physical Properties

Can be observed or measured without changing the substance's identity (e.g., color, density, melting point).

Chemical Properties

Describe how a substance reacts to form other substances (e.g., flammability, reactivity).

Element

A pure substance that cannot be broken down into simpler substances by chemical means.

Compound

Two or more elements chemically combined in fixed proportions (e.g., H2O, CO2).

Homogeneous Mixtures

Uniform composition throughout (e.g., saltwater, air).

Heterogeneous Mixtures

Non-uniform composition; components are visibly separate (e.g., sand and water, oil and water).

Solid

Matter with a definite shape and volume.

Liquid

Matter with a definite volume but takes the shape of its container.

Gas

Matter with no definite shape or volume; expands to fill its container.

Plasma

Ionized gas.

Atomic Number (Z)

The number of protons in an atom; defines the element.

Mass Number (A)

The sum of protons and neutrons in an atom.

Isotopes

Atoms of the same element that have the same atomic number (Z) but different mass numbers (A).

Electromagnetic Spectrum

The range of all types of electromagnetic radiation.

Wave-Particle Duality

The concept that light exhibits properties of both waves and particles.

Pauli Exclusion Principle

No two electrons in an atom can have the same set of four quantum numbers.

Hund's Rule

Electrons fill degenerate orbitals singly before pairing up.

Aufbau Principle

Electrons fill atomic orbitals of the lowest available energy levels before filling higher ones.

Ionic Bonding

The transfer of electrons between a metal and a nonmetal, forming ions and electrostatic attraction.

Covalent Bonding

The sharing of electrons between two nonmetals.

Lewis Structures

Diagrams that show bonding and non-bonding electron pairs.

VSEPR Theory

Predicts molecular geometry based on minimizing electron pair repulsion.

Mole Concept

1 mole = 6.022 x 10^23 particles (Avogadro's number).

Limiting Reactant

The reactant that is consumed first in a chemical reaction, determining the maximum amount of product formed.

Ideal Gas Law

The equation PV = nRT, which relates the pressure, volume, moles of gas, gas constant, and temperature.

Boyle's Law

Describes the inverse relationship between pressure and volume of a gas.

Charles's Law

Describes the direct relationship between the volume and temperature of a gas.

Arrhenius Definition

Acids produce H+ ions in water; bases produce OH- ions in water.

pH Scale

Measures acidity or alkalinity; pH = -log[H+].

Thermochemistry

The study of heat changes associated with chemical reactions.

Exothermic Processes

Processes that release heat to the surroundings.

Endothermic Processes

Processes that absorb heat from the surroundings.

Standard Enthalpy of Formation (ΔHf°)

The enthalpy change when one mole of a compound is formed from its elements in their standard states.

Hess's Law

The total enthalpy change for a reaction is the same regardless of the number of steps or pathway taken from reactants to products.