Key Topics to Study

Elements

Pure substances made of one type of atom (e.g., O₂, Fe).

Diatomics

Molecules made of two atoms of the same element (e.g., H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂).

Compounds

Two or more elements chemically combined in fixed ratios (e.g., H₂O, CO₂).

Mixtures

Combination of two or more substances physically mixed, not chemically combined.

Homogeneous

Uniform composition (e.g., saltwater).

Heterogeneous

Non-uniform composition (e.g., sand in water).

Solutions

Homogeneous mixtures with particles < 1 nm, clear, no Tyndall effect.

Colloids

Heterogeneous mixtures with 1-1000 nm particles that scatter light (Tyndall effect) and are stable.

Suspensions

Heterogeneous mixtures with > 1000 nm particles that settle and may scatter light.

Tyndall Effect

Scattering of light by particles in a colloid or suspension (e.g., milk showing light beam).

Intensive Properties

Properties that do NOT depend on the amount of matter (e.g., density, boiling point).

Extensive Properties

Properties that depend on the amount of matter (e.g., mass, volume).

Qualitative Data

Descriptive data observed with senses (e.g., color, texture).

Quantitative Data

Data measured with numbers (e.g., temperature, mass).

Solid

State of matter with fixed shape and volume, particles tightly packed.

Liquid

State of matter with fixed volume but no fixed shape, particles move more freely.

Gas

State of matter with no fixed shape or volume, particles widely spaced.

Plasma

Ionized gas, high energy, found in stars.

Physical Change

Change that does not affect the substance's chemical structure (e.g., melting ice).

Chemical Change

Change that produces a new substance (e.g., rusting iron).

Physical Separations

Methods that separate based on physical properties (e.g., filtration, evaporation).

Chemical Separations

Methods that break chemical bonds (e.g., electrolysis).

Law of Conservation of Matter

Mass is neither created nor destroyed in physical/chemical changes.

Law of Conservation of Energy

Energy is conserved in all processes.

Paper Chromatography

A technique to separate mixtures based on solubility and movement through paper.