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CH. 15 Classification of Matter
Section 1: Composition of Matter • Substance: • Either an element or a compound • Element: • Substance made of all the same type of atom • Ex: nugget of gold, piece of lead • Compound: • Substance made of two or more types of atoms combined in a fixed proportion • Ex: water (H 20), table salt (Na. Cl)
Section 1: Composition of Matter • Mixture: • Made of 2 or more substances that can be separated by physical means • Heterogeneous mixture: • Mixture of different and easily distinguishable materials (ex: trail mix) • Homogeneous mixture: • Contains 2 or more gaseous, liquid, or solid substances blended evenly • Also called a solution (ex: soft drink)
Section 1: Composition of Matter • Colloid: • Heterogeneous mixture with larger particles that never settle • Colloids scatter light in the Tyndall effect • Ex: paint, fog • Suspension: • Heterogeneous mixture containing a liquid in which visible particles settle • Ex: muddy pond water
Section 2: Properties of Matter • Physical property: • characteristics of a material which can be observed without changing the identity of the substances in the material examples: color, shape, size, melting point, and boiling point • 1. Appearance—physical description of a substance • 2. Behavior—how a substance acts; for example, magnetism, viscosity, ductility • 3. Physical properties such as size and magnetism can be used to separate mixtures.
Section 2: Properties of Matter • Physical change: • change in a substance’s size, shape, or state of matter • substance does not change identity when it undergoes a physical change • Distillation: • a process for separating a mixture by evaporating a liquid and condensing its vapor
Section 2: Properties of Matter • Chemical property: • characteristics of a substance indicating that it can change chemically • for example: • flammability or light sensitivity of a substance
Section 2: Properties of Matter • Chemical Change: • When one substance changes to another substance. • Some chemical changes are indicated by temperature change, smell, or bubble formation. • Other chemical changes occur very slowly such as the formation of rust. • Chemical changes can be used to separate substances such as metals from their ores.
Section 2: Properties of Matter • Weathering of Earth’s surface involves both physical and chemical changes. • Physical—big rocks split into smaller ones; streams carry rock particles from one location to another • Chemical—Chemical changes can occur in rocks when calcium carbonate in limestone changes to calcium hydrogen carbonate due to acid rain.
Section 2: Properties of Matter • Law of Conservation of Mass • Mass of all substances present before a chemical change equals the mass of all substances after the change.