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CHAPTER 17 Get ready to take notes! CLASSIFICATION OF MATTER Composition of Matter I. Substance is either an element or a compound. A. When all the atoms in a substance are alike, the substance is an element. 1. A compound is a substance with two or more elements combined in a fixed proportion.2. Two or more substances that can be easily separated by physical means form a mixture. B. Heterogeneous mixture mixture of different & easily distinguishable materials. 1. Homogeneous mixture •contains 2 or more gaseous, liquid, or solid substances blended evenly. •also called a solution. 2. Colloid - heterogeneous mixture with larger particles that never settle. 3. Colloids scatter light in the Tyndall effect. 3. A heterogeneous mixture containing a liquid in which visible particles settle is called a suspension.4. Properties of Matter II. Physical property characteristic of a material which can be observed without changing the identity of the substances in the material. Ex: A. shape, e siz , melting point, and boiling point. Appearance - physical description of a substance. 1. Behavior - how a substance acts. ductility magnetism viscosity 2. Physical properties such as size and magnetism can be used to separate mixtures. 3. Physical change change in a substance’s size, shape, or state of matter. B. A substance does not change identity when it undergoes a physical change. 1. Distillation is a process for separating a mixture by evaporating a liquid and condensing its vapor. 2. Chemical property characteristics of a substance indicating that it can change chemically. Ex: C. flammability light sensitivity When one substance changes to another substance, a chemical change has occurred. fD. Some chemical changes are indicated by temperature change, smell, or bubble formation. 1. Other chemical changes occur very slowly such as the formation of rust. 2. Chemical changes can be used to separate substances such as metals from their ores. 3. Weathering of Earth’s surface involves both physical and chemical changes. E. Physical changes cause big rocks to split into smaller ones; streams carry rock particles from one location to another. 1. Chemical changes can occur in rocks when calcium carbonate in limestone changes due to acid rain. 2. Law of Conservation of Mass - Mass of all substances present before a chemical change equals the mass of all substances after the change. F. THE END