Chapter 3 Matter – Properties and Changes Section 3.1: Properties of Matter Objectives Identify the characteristics of a substance. Distinguish between physical & chemical properties. Differentiate among the physical states of matter. Organization of Matter Matter Substance Element Compound Mixture Homogeneous Heterogeneous Substances Matter (anything that has mass & takes up space) that has a uniform and unchanging chemical composition is called a substance or a pure substance. Examples: Water (H2O) Salt (NaCl) NOT saltwater! Physical Properties A physical property is a characteristic that can be observed without changing the chemical composition of a sample of matter. Because substances have an unchanging composition, the physical properties of substances are constant from one sample to another. Some of them may be used to identify the substance. Examples: color, shape, mass, odor, taste, hardness, density, state, solubility, melting point, boiling point. Extensive or Intensive? Extensive physical properties are dependent on the AMOUNT of substance that is present. Mass and length are examples. Intensive physical properties are independent of the amount of substance present. The density of a substance does not depend on how much is present. PRACTICE: Classify the physical properties listed previously as extensive or intensive. Practice Problem - List the physical properties of the following: Observing Properties PHYSICAL PROPERTIES •Appropriate observations would include: •White color •Small, crystalline particles •Particles are lustrous; long rectangular shape. •Inappropriate observations: •Looks like salt Chemical Properties A chemical property is a property of a substance that cannot be observed unless the substance has changed its chemical composition. Chemical reactivity or the ability/inability of a substance to react with another substance is a chemical property. Other chemical properties are the ability/inability to oxidize (combine with oxygen), & flammability (the ability to ignite). Observing Properties CHEMICAL PROPERTIES Appropriate observations include: Inappropriate observations: Calcium Combines readily with oxygen Reacts vigorously with water Rusts Dissolves in water Observing Properties Important note: The properties that are observed will depend on environmental conditions. For example, water is a liquid at certain temperatures and a solid or gas at others. Therefore, it is necessary to record the temperature & pressure of the environment when observations of properties are made. States of Matter The physical state of a substance is one of its physical properties. Matter can exist in one of 4 physical forms: solid, liquid, gas, or plasma. Plasma occurs naturally on Earth only in lightning. Distinguishing States of Matter State Shape Volume Solid Has its own shape; a definite shape Has a definite Very close together; not volume Liquid Distance between particles compressible Takes the shape Has a definite Less closely packed, able to of its container; volume flow, still indefinite shape incompressible Gas Takes the shape Takes the volume of its container; of its container; indefinite volume indefinite shape Very far apart; easily compressed Gas vs. Vapor These words do not mean the same thing. A gas is a substance that exists naturally in the gaseous state at room temperature. A vapor is a substance in the gaseous state that is naturally a solid or liquid at room temperature. Steam is a vapor. It is often simply called water vapor.