Basic Chemistry Concepts: Atoms, Molecules, and Matter

Atom

The smallest chemically indivisible fundamental particle of matter; atoms are neutral.

Molecule

The smallest chemical entity that can exist discretely in nature; it may contain one or more atoms.

Ion

A charged entity formed by gaining or losing electrons; it may contain one or more atoms.

Scientific Approach

A systematic process of inquiry used to understand a phenomenon, solve real-world problems, or address knowledge gaps.

Observation

Information gathered by observing a phenomenon; it can be qualitative or quantitative.

Experiment

A highly controlled procedure designed to generate observations or data that confirm or refute a hypothesis.

Qualitative Observation

An observation describing how a process happens without measuring it numerically.

Quantitative Observation

An observation that measures or quantifies something about a process.

Hypothesis

A tentative interpretation or explanation of observations that makes predictions that can be tested.

Falsifiable

Able to be proven or disproven through testing or experimentation.

Scientific Law

A brief statement that summarizes past observations and predicts future ones; it describes what happens during a phenomenon.

Scientific Theory

An explanation of both what happens and why it happens in nature, including the underlying reasons or mechanisms.

Matter

Anything that occupies space and has mass.

Physical State

The physical form in which matter exists, such as solid, liquid, or gas.

Solid

A state of matter in which particles are closely packed in fixed locations, giving it a fixed volume and rigid shape.

Liquid

A state of matter in which particles are close together but can move relative to one another; it has a fixed volume but no fixed shape.

Gas

A state of matter in which particles have a lot of space between them, move freely, and are compressible; it has no fixed volume or shape.

Crystalline Solid

A solid whose particles are arranged in a regular, repeating pattern.

Amorphous Solid

A solid whose particles are arranged irregularly rather than in a regular repeating pattern.

Pure Substance

Matter made up of only one component with a fixed composition.

Mixture

Matter composed of two or more chemically distinct components in varying proportions.

Element

A pure substance composed of atoms of the same identity that cannot be chemically broken down into simpler substances.

Compound

A pure substance made of atoms of different elements that can be chemically broken down into simpler substances.

Heterogeneous Mixture

A mixture whose components can be identified with the naked eye or with a microscope.

Homogeneous Mixture

A mixture whose components cannot be identified with the naked eye or with a microscope because they are mixed uniformly.

Solution

A homogeneous mixture in which the components are uniformly mixed.

Physical Separation

Separating a mixture into its components using physical techniques without chemically changing the components.

Decantation

A separation technique in which a mixture is allowed to settle and one component is carefully poured away from another.

Filtration

A separation technique that uses a filter to separate components of a mixture.

Distillation

A separation technique that heats a mixture so that a component with a lower boiling point vaporizes and can be separated.

Physical Change

A change that alters only the state or appearance of a substance; no new substance is formed and its composition/identity remains unchanged.

Chemical Change

A change in the chemical identity or composition of a substance in which a new substance with a different nature is formed.

Physical Property

A characteristic of a substance that can be observed or measured without changing the substance's chemical identity.

Chemical Property

A characteristic describing how a substance can undergo a chemical change or react to form new substances.

Law of Conservation of Mass

The principle that matter is neither created nor destroyed in a chemical reaction.