Chapter 2

Classification of Matter

Classification of Matter Concept Map

Pure Substances

Composition ConstantElement (one kind of atom)Compound (two or more atoms

chemically combined)

Mixtures of Matter

Mixture- a combination of two or more pure substances in which each pure substance retains its individual chemical properties.

Composition is variable - (the number of mixtures that can be created by combining substances is infinite)

Types of Mixtures

Homogeneous MixturesHas a constant composition throughoutAlso called a “solution” (i.e., salt water)

Heterogeneous Mixtures Do not blend smoothly throughout and in which

the individual substances remain distinct.Examples: mixture of sand and water, fresh-

squeezed orange juice, pizza

Types of Solutions (Homogeneous)Solid-solid (alloy-steel)Solid-liquid (sugar in water)Liquid-liquid (vinegar = acetic acid + water)

Liquid-gas (water vapor in air)Gas-liquid (carbonated drinks)Gas-gas (air is a mixture of nitrogen, oxygen,

argon)Gas-solid - styrofoam

Types of Heterogeneous Mixtures

Colloid- contains tiny particles that do not settle (i.e., homogenized milk, gelatin)

Suspension- contains larger particles that eventually settle out. Particles have to be re-suspended. (i.e., chocolate milk, orange juice)

Techniques for Separating MixturesFiltration- uses a porous barrier to

separate a solid from a liquid

Techniques for Separating MixturesDistillation- A mixture is heated until the

substance with the lowest boiling point boils to a vapor that can then be condensed into a liquid and collected.

Techniques for Separating MixturesCrystallization - separation technique that

results in the formation of pure solid particles of a substance from a solution containing the dissolved substance.

Techniques for Separating MixturesChromatography- separates the

components of a mixture (called the mobile phase) on the basis of the tendency of each to travel or be drawn across the surface of another material (called the stationary phase).

A magnet can be used to separate magnetic particles from others (Ex. separate sand and iron filings using a magnet to extract the iron based on physical property of magnetism)

Properties & Changes in Matter

Physical Properties Physical ChangesChemical Properties Chemical ChangesPhysical and chemical properties

depend on temperature and pressure.

Physical Properties

Can be observed or measured without changing the substance’s identity.

Ex. Density, color, odor, taste, hardness, melting point, boiling point, solubility, state of matter (s,l,g), temperature

Physical Changes

Changes that may dramatically alter the appearance yet leave the composition unchanged

Examples: split, bend, crush, grind, changes in state of matter (boil, freeze, condense, vaporize, melt), sharpening a pencil, cutting a sheet of paper, breaking a crystal, crumpling a piece of paper

Chemical Properties

The ability of a substance to combine with or change into one or more other substances having different properties.

Examples: FlammableSupports combustionthe ability of iron to rust when exposed to airInability of iron to react with nitrogen gas at

room temp.

Chemical ChangesA process that involves one or more substances

changing into new substancesCommonly referred to as a chemical reaction Examples:

Fermentation of grape juiceRustingExplodingOxidizingCorrodingTarnishingBurningRotting