Physical Science 100: Exam 3 Review

Comprehensive vocabulary flashcards covering the key concepts from Physical Science 100 Exam 3 Review, including thermodynamics and entropy, chemical equations, bond types (metallic, ionic, covalent), intermolecular forces, fatty acids, silicates, and nuclear processes.

Entropy

A quantitative measure of disorder or randomness in a physical system or the universe.

Law of Increasing Disorder

A physical law stating that energy in the universe cannot be created or destroyed, only transferred between forms, and the total entropy of the universe is always increasing as energy degrades into less useful forms.

Reversible Process

An ideal, rare process that does not increase the entropy of the universe and can be undone without adding energy, such as a frictionless swinging pendulum or ice and water coexisting at equilibrium at $0\,^\circ\text{C}$.

Irreversible Process

A natural process that increases the entropy of the universe and cannot be reversed without the input of external energy; encompasses nearly all physical and chemical processes.

Thermal Energy

The least ordered, highest-entropy form of energy, characterized by the disordered internal kinetic motion of particles and considered practically worthless for efficient work conversion.

Coefficient

A number placed in front of a chemical formula in an equation specifying how many separate molecules or formula units are involved in the reaction.

Subscript

A small number placed below and to the right of an element's symbol in a formula indicating how many atoms of that specific element are chemically bonded together within that molecule.

Diatomic Molecules

Molecules composed of two identical atoms bonded together; the elements that naturally exist this way are $\text{H}_2$, $\text{N}_2$, $\text{F}_2$, $\text{O}_2$, $\text{I}_2$, $\text{Cl}_2$, and $\text{Br}_2$ ('Have No Fear Of Ice Cold Beer').

Molecular Family

A group of molecules that share a related structural pattern or repeating chemical unit, such as alkanes.

Mass Spectrometry

An analytical method used to measure the mass-to-charge ratios of ions in a sample, identifying the Most Common Fragment (MCF) by the tallest peak and the Molecular Mass (MM) by the rightmost significant peak.

Activation Energy

The minimum energy input necessary to initiate a chemical reaction.

Exothermic Reaction

A reaction where energy exits the system and is released to the surroundings, placing the product energy level below the reactant energy level on an energy coordinate diagram and releasing heat or light.

Endothermic Reaction

A reaction where energy enters the system from the surroundings, resulting in products with higher potential energy than the reactants and causing the surroundings to cool.

Catalyst

A substance that accelerates a reaction by lowering the activation energy barrier without affecting the chemical identities or energy levels of the reactants and products.

Metallic Bond

A bond between metal atoms characterized by a shared 'sea of electrons,' where valence electrons are delocalized across overlapping atomic orbitals throughout a network solid.

Malleability

The mechanical property of metals to bend, stretch, and deform under stress without fracturing because delocalized electrons continuously adjust to keep atomic nuclei bonded together.

Band Gap

The forbidden energy zone between the filled valence band and the empty conduction band that determines the electrical conductivity and optical absorption of a material.

Semiconductor

A material possessing a moderate band gap that restricts electron conductivity at low temperatures, but increases in conductivity as heat or energy promotes electrons into the conduction band.

Alloy

A metallic material formed by blending two or more metals (or a metal and a nonmetal, such as steel), generally lowering thermal and electrical conductivity while significantly increasing structural hardness and strength.

Ionic Bond

A chemical bond formed between a metal and a nonmetal involving the transfer of electrons due to large differences in electronegativity, creating oppositely charged ions held together in a network solid by electromagnetic attraction.

Brittleness (Ionic Compounds)

The tendency of an ionic solid to shatter when subjected to force because a shear displacement aligns ions of like charges ($+/+$ and $-/-$), generating repulsive forces that split the crystal.

Ionic Conductor

A substance that does not conduct electricity as a solid because ions are locked in place, but readily conducts electricity when dissolved or melted into a liquid with free-moving charged ions.

Covalent Bond

A chemical bond formed between nonmetal atoms sharing pairs of valence electrons in localized molecular orbitals, resulting in discrete molecular matter.

Electronegativity

A chemical property measuring an atom's attraction for electrons within a shared covalent bond.

Intermolecular Forces

Relatively weak non-covalent forces of attraction occurring between separate molecules, determining physical properties such as melting and boiling points.

Intramolecular Forces

Strong chemical forces (such as covalent bonds) that bond individual atoms together inside a single molecule.

Polar Molecule

A molecule possessing an asymmetric spatial shape and uneven electron charge distribution, creating permanent partial positive ($\delta^+$) and partial negative ($\delta^-$) poles.

Nonpolar Molecule

A molecule characterized by symmetric charge distribution or identical electronegativities, displaying no permanent electrical dipole.

Hydrogen Bond

A strong dipole-dipole intermolecular attraction occurring when hydrogen is directly bonded to an electronegative atom of nitrogen ($\text{N}$), oxygen ($\text{O}$), or fluorine ($\text{F}$) and interacts with a lone pair on an adjacent polar molecule.

Dipole-Dipole Interaction

An intermolecular attraction between the permanently positive end of one polar molecule and the permanently negative end of another polar molecule.

Dispersion Forces

Weak, transient intermolecular forces caused by instantaneous, random fluctuations of electron clouds producing temporary dipoles; present in all molecules and the only intermolecular force in nonpolar molecules.

Saturated Fatty Acid

A fatty acid chain with zero carbon-carbon double bonds, resulting in a straight geometry that packs tightly, giving it the highest melting point and making it solid at room temperature.

Trans Fatty Acid

An unsaturated fatty acid containing a double bond configured in a straight conformation, allowing it to pack compactly like saturated fats and remain semi-solid or solid at room temperature.

Monounsaturated Fatty Acid

A fatty acid chain containing exactly one carbon-carbon double bond that creates a kink or bend, disrupting tight molecular packing and producing a low melting point (liquid at room temperature).

Polyunsaturated Fatty Acid

A fatty acid chain possessing two or more double bonds that cause multiple bends, yielding the weakest intermolecular interactions and lowest melting point (liquid at room temperature).

Silicate Minerals

A mineral group based on silicon-oxygen structures that form sheets (flaking physically into plates, like mica), three-dimensional networks (yielding hard chunks or crystals, like quartz), or linear chains (forming fibrous strings, like asbestos).

Strong Nuclear Force

The short-range, powerful fundamental force that overcomes electrostatic repulsion to hold protons and neutrons together within an atomic nucleus, remaining stable only up to the size of an iron nucleus.

Nuclear Fission

A nuclear reaction in which a massive, unstable atomic nucleus (such as $\text{Uranium-238}$) splits into two or more smaller nuclei, releasing energy and subatomic particles.

Nuclear Fusion

A nuclear process naturally powering stars like the Sun in which two light nuclei combine under extreme conditions to create a single heavier nucleus, yielding substantial energy.

Mass-Energy Equivalence ($E=mc^2$)

The principle stating that mass and energy are interchangeable; whenever the average mass per nucleon drops in a nuclear reaction, that missing mass is converted and released as energy.

Alpha Decay ($\alpha$ Decay)

A type of radioactive decay in which an unstable nucleus ejects an alpha particle ($^4_2\text{He}$), reducing the parent nucleus by 2 protons and 2 neutrons.

Beta Decay ($\beta$ Decay)

A type of radioactive decay in which a nuclear neutron transforms into a proton while emitting a high-speed beta particle (an electron, $^0_{-1}e$), increasing the atomic number by 1 while keeping the mass number unchanged.

Gamma Decay ($\gamma$ Decay)

A radioactive decay process where an excited nucleus transitions to a lower energy state by releasing high-energy electromagnetic radiation ($^0_0\gamma$ photon) without altering the mass number or atomic number.

Half-Life

The duration of time required for one-half of the radioactive nuclei in an unstable sample to spontaneously decay.