Chemistry Form 3: Pure Substances, Mixtures, and the Particulate Theory of Matter

Matter

Anything that has mass and occupies space, existing commonly in three states: solid, liquid, and gas.

Particle Diagram

A visual model that uses shapes, dots, or circles to represent atoms, molecules, or ions at a microscopic level, illustrating how particles are arranged, spaced, and bonded.

Pure Substance

A form of matter composed of only one type of material that has a constant, fixed composition, uniform properties throughout, and component parts that cannot be separated by physical means.

Element

A pure substance that cannot be broken down into any simpler substances by any ordinary chemical or physical means, composed of only one type of atom.

Atom

The smallest particle in an element that possesses the same properties as that element.

Monatomic Element

An element composed of singular, unbonded atoms, such as gold ($\text{Au}$).

Molecular Element

An element composed of two or more of the same atoms chemically bonded together, such as hydrogen ($\text{H}_2$), oxygen ($\text{O}_2$), chlorine ($\text{Cl}_2$), or ozone ($\text{O}_3$).

Compound

A pure substance containing two or more different types of elements chemically bonded together in fixed proportions, which can be broken down chemically into its component elements.

Mixture

A physical combination of two or more substances (elements and/or compounds) where each retains its own chemical identity and individual properties, possessing a variable composition that can be separated by physical means.

Homogeneous Mixture

A mixture in which the components are evenly distributed throughout, cannot be distinguished from each other, and present identical composition and properties across all regions.

Solution

A homogeneous mixture of a solute dissolved in a solvent that appears as one substance, where the components are not chemically bonded.

Solvent

The major component of a solution that does the dissolving (such as water in a sugar solution).

Solute

The minor component of a solution that gets dissolved by the solvent (such as sugar in water).

Aqueous Solution

A solution in which water serves as the solvent.

Heterogeneous Mixture

A mixture in which the components are not evenly distributed throughout, retain their own separate qualities, and can usually be distinguished visually.

Colloid

A heterogeneous mixture where microscopic particles between $1\,\text{nm}$ and $1000\,\text{nm}$ in diameter are spread evenly through another substance, do not settle out on standing, cannot be separated by filtration, and scatter light.

Suspension

A heterogeneous mixture containing large particles greater than $1000\,\text{nm}$ in diameter that do not dissolve, are visible to the naked eye, settle out upon standing, and can be separated by filtration.

Paper Chromatography

An analytical method used to test purity, in which a pure substance produces a single spot on a chromatogram, whereas an impure substance produces two or more spots.

Particulate Theory of Matter

The theory stating that all matter is made of tiny particles (atoms, molecules, or ions) separated by spaces, in constant random motion, attracting one another, and gaining kinetic energy when heated.

Diffusion

The movement of particles from a region of higher concentration to a region of lower concentration until they become evenly distributed, driven by continuous random motion.

Osmosis

The movement of water molecules only through a differentially permeable (selectively permeable) membrane from a region of higher water concentration to a region of lower water concentration until equilibrium is reached.

Brownian Motion

The random zigzag movement shown by particles suspended in a fluid, caused by continuous collisions with the moving particles of the fluid.

Physical Property

A characteristic of a substance that can be observed and measured without changing it into another substance, such as colour, density, melting point, boiling point, electrical conductivity, and hardness.

Physical Change

A change