1 The Composition of Matter - Vocabulary Flashcards

Vocabulary-style definitions of key terms from the lecture notes on matter, states, changes, mixtures, and the periodic table.

States of matter

The four fundamental states: solid, liquid, gas, and plasma; determined by particle arrangement and response to temperature and pressure.

Solid

Definite shape and volume; tightly packed particles with strong intermolecular forces; high density; low compressibility.

Liquid

Definite volume, indefinite shape; weaker intermolecular forces; flows; has viscosity; moderate compressibility.

Gas

No fixed shape or volume; expands to fill container; very weak intermolecular forces; high particle speeds; high compressibility; low density.

Plasma

Ionized gas with free-moving ions and electrons; highly conductive; found in stars and lightning.

Phase transition

Change from one state of matter to another, often involving energy transfer (e.g., melting, freezing, evaporation, condensation, sublimation, deposition).

Melting

Solid to liquid transition; occurs when a solid gains energy at a constant temperature.

Freezing

Liquid to solid transition; removal of energy at a constant temperature.

Evaporation

Liquid to gas transition; energy input; includes boiling as rapid evaporation at higher heat.

Condensation

Gas to liquid transition; vapor cools and forms droplets.

Sublimation

Solid to gas transition without a liquid phase.

Deposition

Gas to solid transition without a liquid phase.

Latent heat of fusion

Energy required to change a solid to a liquid at a constant temperature; temperature remains constant during the phase change.

Latent heat of vaporisation

Energy required to change a liquid to a gas at a constant temperature; temperature remains constant during the phase change.

Heterogeneous system

Non-uniform composition with two or more phases; distinct boundaries; components can be separated by physical means.

Homogeneous system

Uniform composition with a single phase; no visible boundaries; components thoroughly mixed.

Colloid

Intermediate between homogeneous and heterogeneous; microscopically dispersed particles that do not settle; examples: milk, fog, gelatin, mayonnaise.

Suspension

Heterogeneous mixture with larger particles that eventually settle; requires stirring to stay mixed.

Solution

Homogeneous mixture where a solute is dissolved in a solvent; examples include saltwater and sugar in tea.

Solvent

Substance in which a solute is dissolved; e.g., water in saltwater.

Solute

Substance dissolved in a solvent; e.g., salt in saltwater.

Alloy

Homogeneous solid mixture of two or more elements, usually metals (e.g., steel, brass).

Crystal

Solid with an ordered, repeating arrangement of atoms; examples include diamonds and graphite.

Element

Pure substance consisting of only one type of atom; cannot be broken down by chemical means; represented by a symbol; found on the periodic table.

Compound

Pure substance made of two or more different elements chemically bonded; fixed chemical formula; can only be separated by chemical reactions.

Pure substance

Matter with a fixed composition that is either an element or a compound.

Metal

Element that is a good conductor of heat and electricity; usually shiny, malleable, and ductile.

Nonmetal

Elements that are poor conductors; brittle; may be gases or solids; examples include O, C, S.

Metalloid

Element with properties intermediate between metals and nonmetals (e.g., silicon, boron).

Noble gas

Inert gases that are generally nonreactive; used in signs and lighting (e.g., He, Ne, Ar).

Periodic Table

Organization of elements by increasing atomic number; arranged in groups and periods with recurring properties.

Atomic number

Number of protons in the nucleus of an atom; identifies the element.

Symbol

Abbreviated code for an element (e.g., H, Fe, Na).

Atomic mass

Average mass of atoms of an element, measured in atomic mass units (amu).

Allotrope

Different structural forms of the same element (e.g., O2 and O3; carbon as graphite and diamond).

Molecular compound

Compound formed by covalent bonding; nonmetals share electrons (e.g., H2O, CO2).

Ionic compound

Compound formed by transfer of electrons between metals and nonmetals; ionic bonds (e.g., NaCl, CaCO3).

Decomposition

Chemical change where a compound breaks down into simpler substances (e.g., HgO → Hg + O2).

Physical change

Change in matter that does not alter composition (e.g., melting, freezing).

Chemical change

Change that produces new substances with different properties (e.g., combustion, oxidation).

Group (periodic table)

A column in the periodic table; elements in a group have similar chemical properties.

Period (periodic table)

A row in the periodic table; properties change across a period as electrons are arranged.