Chemistry: Pure Substances and Mixtures

Pure Substances

Matter with a definite or fixed composition, made up of a specific number of atoms or groups of atoms.

Elements

The simplest form of matter made up of one kind of atom, cannot be decomposed into simpler forms.

Periodic Table of Elements

A chart that organizes all known elements and helps identify those with similar properties.

Metals

Solid at room temperature, lustrous, malleable, ductile, and best conductors of heat and electricity.

Nonmetals

Opposite of metals; can be gaseous or solid, and typically do not conduct heat or electricity well.

Metalloids/Semimetals

Exhibit properties of both metals and nonmetals; conduct heat and electricity but not as well as metals.

Compounds

Substances composed of two or more different elements combined in a fixed ratio through a chemical reaction.

Mixtures

Combinations of two or more pure substances that retain their individual properties and are not chemically combined.

Homogeneous Mixture

A mixture with evenly distributed components that cannot be distinguished by the naked eye.

Solution

A homogeneous mixture consisting of a solute dissolved in a solvent.

Solute

The substance that is dissolved in a solution, present in smaller amounts.

Solvent

The medium in which the solute is dissolved, present in larger amounts.

Heterogeneous Mixture

A mixture where components are not evenly distributed and can be distinguished by the naked eye.

Colloids

A heterogeneous mixture with particles larger than those in solutions but smaller than in suspensions; exhibit the Tyndall effect.

Suspension

A heterogeneous mixture with large particles that can be seen and will settle at the bottom due to gravity.

Colloids

A heterogeneous mixture with particles larger than those in solutions but smaller than in suspensions; exhibit the Tyndall effect.

Types of Colloids

Colloids can be classified into various types based on the phases involved, such as aerosols (gas in liquid or solid), emulsions (liquid in liquid), foams (gas in liquid), sols (solid in liquid), and gels (liquid in solid).

Brownian Motion

The random movement of colloidal particles suspended in a fluid, resulting from collisions with the molecules of the fluid.

Tyndall Effect

The scattering of light by particles in a colloid, which makes the path of the light visible; responsible for the visible beam of light in a foggy or dusty environment.

Saturation

The point at which a solution can no longer dissolve additional solute at a given temperature and pressure.

Saturation Point

The maximum amount of solute that can be dissolved in a solvent at a specific temperature and pressure.

Unsaturated Solution

A solution that contains less solute than the saturation point, allowing more solute to be dissolved.

Saturated Solution

A solution that contains the maximum amount of solute that can be dissolved at a specific temperature and pressure.

Supersaturated Solution

A solution that contains more solute than can normally be dissolved at a given temperature; it is unstable and may precipitate out excess solute.