Honors Chemistry Unit 2: Matter & Atomic Theory

Vocabulary practice flashcards covering states of matter, physical and chemical properties, foundational atomic theories and experiments, isotopes, and nuclear decay modes from Unit 2 Honors Chemistry.

Solids

A state of matter that has a definite shape and definite volume, with particles tightly packed together in a rigid, fixed structure that only vibrate in place.

Liquids

A state of matter that has an indefinite shape (takes the shape of the container) but a definite volume, with particles close together that can slide and flow past one another.

Gases

A state of matter that has an indefinite shape and indefinite volume, with particles that are very far apart, move rapidly, and expand to completely fill whatever container they occupy.

Extensive Properties

Properties that depend on the amount of matter present in a sample, such as mass, volume, length, and total energy.

Intensive Properties

Properties that depend solely on the type of matter or identity of the substance rather than the amount, such as density, boiling point, melting point, color, and conductivity.

Physical Properties

Characteristics that can be observed or measured without altering the substance's chemical identity, such as density and color.

Chemical Properties

Characteristics describing a substance's ability to undergo a chemical change that transforms it into a completely new substance, such as flammability and reactivity with acid.

Physical Changes

Changes that alter the physical state or appearance of a substance without altering its chemical composition, such as boiling water or dissolving sugar.

Chemical Changes

Processes involving a chemical reaction where new substances with entirely new chemical compositions and properties are formed, such as burning wood or iron rusting.

Law of Conservation of Mass

A fundamental law stating that mass is neither created nor destroyed during an ordinary chemical reaction; total starting mass equals total final mass.

Law of Definite Proportions

A law stating that a specific chemical compound always contains exactly the same elements in the exact same mass proportions, regardless of the sample's size or source.

Law of Multiple Proportions

A law stating that if two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are always in ratios of small whole numbers (e.g., $CO$ vs $CO_2$).

Cathode Ray

A glowing beam traveling from the negative electrode to the positive electrode in a low-pressure gas tube, which J.J. Thomson demonstrated was composed of streams of tiny, negatively charged subatomic particles called electrons.

Plum Pudding Model

An atomic model proposed by J.J. Thomson visualizing the atom as a spherical cloud of uniform positive charge containing small, negatively charged electrons scattered throughout it like chocolate chips in cookie dough.

Gold Foil Experiment

Ernest Rutherford's experiment firing fast-moving, positively charged alpha ($\alpha$) particles at thin gold foil; most passed through undeflected, but about $1\text{ in }8{,}000$ deflected sharply, revealing a dense, positively charged nucleus.

Nuclear Model

Rutherford's atomic model establishing that an atom is mostly empty space with an incredibly dense, minuscule, positively charged core at its center called the nucleus.

Isotope

Atoms of the same element that have the identical number of protons but a different number of neutrons, resulting in a different mass number.

Hyphen Notation

A method of specifying an isotope written as 'Element Name - Mass Number' (such as Carbon-14), indicating the element's identity and its total number of protons plus neutrons.

Nuclear Notation

A method of specifying an isotope displaying the chemical symbol with the Mass Number ($A$) at the top left, the Atomic Number ($Z$) at the bottom left, and any ionic charge.

Alpha ($\alpha$) Radiation

A type of nuclear radiation that emits a helium nucleus ($^4_2\text{He}$) consisting of $2$ protons and $2$ neutrons; it has low penetrating power (stopped by paper), decreases mass number by $4$, and decreases atomic number by $2$.

Beta ($\beta$) Radiation

A type of nuclear radiation that emits a high-energy electron ($^0_{-1}\text{e}$) formed from a decaying neutron; it has moderate penetrating power (stopped by aluminum foil), causes no change in mass number, and increases atomic number by $1$.

Gamma ($\gamma$) Radiation

A type of nuclear radiation that emits high-energy electromagnetic waves ($^0_0\gamma$); it has high penetrating power (requires thick lead or concrete to stop) and causes no change in mass number or atomic number.