Chemistry: Matter, Changes, and Chemical Bonding

Vocabulary flashcards covering chemical vs. physical changes, evidence of reactions, elements, compounds, mixtures, valence electrons, the octet rule, and types of chemical bonds (ionic, covalent, metallic).

Chemical Reaction

A process where one or more molecules interact, causing bonds between atoms to be broken and created to form new molecules.

Unexpected Color Change

An indicator of a chemical reaction occurring because new molecules radiate light differently, producing new colors.

Unexpected Temperature Change

An indicator of a chemical reaction where energy is absorbed or released during chemical bonding, making the surroundings hotter or colder.

Combustion/Burning

A chemical reaction between substances, usually involving oxygen, accompanied by the generation of heat and light.

Precipitate

A solid that suddenly appears in a solution during a chemical reaction and either settles to the bottom or makes the solution cloudy.

Bubbles

An evidence of a chemical reaction that occurs when gases produced during the reaction are released.

Physical Change

A change that does not change a substance into anything new, such as altering the state of matter, color, temperature, shape, or texture.

Chemical Change

A change where one or more substances fuse to form new substances with new chemical properties (such as iron rusting, gas burning, or eggs cooking).

Matter

Everything around you that has mass and takes up space, existing as a solid, liquid, gas, plasma, or BEC.

Element

A pure substance containing only one kind of atom that is homogeneous throughout and cannot be broken down into simpler materials except by nuclear reactions.

Compound

A pure substance containing two or more kinds of atoms chemically combined, which cannot be separated by physical means and has properties different from its component elements.

Molecule

A group of two or more atoms bonded together representing the smallest unit of a chemical compound or element.

Mixture

A physical combination of two or more elements or compounds that are not chemically combined, retain their individual properties, and can be separated by physical means.

Homogeneous Mixture

A mixture that is uniform all the way through, also known as a solution.

Heterogeneous Mixture

A non-uniform mixture of substances.

Valence Electrons

Electrons located on the outermost energy level (shell) of an atom that determine its chemical reactivity.

Periodic Table

An arrangement of all known chemical elements organized in order of increasing atomic number.

Metals

Elements that are solid at room temperature (except mercury), ductile, malleable, good conductors, and have high melting points.

Nonmetals

Elements characterized as poor conductors (insulators), brittle, dull, with low densities and low melting points.

Metalloids

Elements that exhibit properties of both metals and nonmetals.

Octet Rule

The rule stating that an atom is most stable ("happy") when it has an octet of $8$ electrons in its valence orbital, achieved by gaining, losing, or sharing electrons.

Energy Levels

Layers in the electron cloud where electrons exist: level 1 holds up to $2\,e^-$, level 2 holds up to $8\,e^-$, and level 3 holds up to $18\,e^-$.

Covalent Bond

A chemical bond formed by the sharing of electron pairs between nonmetal atoms without producing ions.

Properties of Covalent Compounds

Substances that exist as gases, liquids, and solids; are bad conductors (insulators); are brittle and flammable; have low melting and boiling points; and are insoluble in water.

Ionic Bond

A chemical bond formed by the transfer of electrons between a metal and a nonmetal, forming oppositely charged ions that attract.

Ion

A charged particle formed when an atom gains or loses electrons.

Properties of Ionic Compounds

Substances that form solid crystal lattices at room temperature, are soluble in water, conduct electricity, and have high melting and boiling points.

Metallic Bond

A chemical bond formed between metal atoms that accounts for metallic properties such as conductivity, ductility, luster, and malleability.