Chapter 2 Classification of Matter

Classification of Matter Concept Map

Pure Substances Composition Constant Element (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 Mixtures Heterogeneous Mixtures Has a constant composition throughout Also 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 Mixtures Filtration- uses a porous barrier to separate a solid from a liquid

Techniques for Separating Mixtures Distillation- 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 Mixtures Crystallization - separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance.

Techniques for Separating Mixtures Chromatography- 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 Changes Chemical Properties Chemical Changes Physical 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: Flammable Supports combustion the ability of iron to rust when exposed to air Inability of iron to react with nitrogen gas at room temp.

Chemical Changes A process that involves one or more substances changing into new substances Commonly referred to as a chemical reaction Examples: Fermentation of grape juice Rusting Exploding Oxidizing Corroding Tarnishing Burning Rotting