CHEM 110: Chemical and Physical Changes & Evidence of Atoms

Vocabulary flashcards covering chemical formulas, classifications of matter, the law of definite proportions, states of matter, phase changes, and particle-level models of physical and chemical transformations from CHEM 110 Discussion Section 03.

Chemical Formula

A representation for a substance that indicates the number of atoms of each element that make up the smallest possible particle of that substance.

Element

A substance consisting of only one type of atom, such as $Ag$ or $O_2$, which cannot be broken down into simpler substances by chemical means.

Compound

A substance composed of atoms of two or more different elements chemically combined in fixed proportions, such as $H_2O$, $CH_4$, $N_2O$, or $C_{12}H_{22}O_{11}$.

Hydrocarbon

A molecule containing only hydrogen and carbon atoms.

Law of Definite Proportions

Also known as the law of constant composition; states that all samples of a given chemical compound always contain the same elements in the exact same proportion by mass.

Physical Transformation

A change in which the chemical identity of the substance is unchanged, altering only its phase, state, or physical form.

Chemical Transformation

A change in which a substance's identity is altered, resulting in the conversion of the substance into one or more new substances.

Solid

A state of matter characterized by particles packed closely together in a rigid, fixed arrangement with definite shape and volume.

Liquid

A state of matter characterized by particles that remain in close contact with one another but are free to move and slide past each other, taking the shape of their container while maintaining a definite volume.

Gas

A state of matter characterized by widely separated particles in continuous, random motion that expand to fill the entire volume and shape of their container.

Melting

The phase transition from a solid to a liquid.

Freezing

The phase transition from a liquid to a solid.

Vaporization

The phase transition from a liquid to a gas.

Condensation

The phase transition from a gas to a liquid.

Sublimation

The direct phase transition from a solid to a gas without passing through the intermediate liquid state.

Deposition

The direct phase transition from a gas to a solid without passing through the intermediate liquid state.

Particle Models of States of Matter

Submicroscopic representations showing the arrangement of matter: liquid (left, touching but disordered at the bottom), gas (middle, widely dispersed particles filling the container), and solid (right, closely packed organized cluster).

Phase Change Diagram of Matter

A diagram mapping the transitions between the three states of matter (solid, liquid, and gas) along with the six corresponding phase changes represented by directional arrows.

Particle Model of a Physical Transformation

A submicroscopic representation showing gas-phase triatomic molecules condensing into a liquid state without altering the molecular identity or bonding of the individual molecules.

Particle Model of a Chemical Transformation

A submicroscopic representation showing bonds breaking and forming between atoms, converting a hetero-diatomic compound into two distinct homonuclear diatomic elemental substances.