Honors Chemistry Chapter 2 Matter and Change • Matter – anything that has mass and takes up space • Mass- amount of matter an object contains • Materials – differ in type of matter they are composed of The Properties of Matter • Extensive properties – depend on the amount of matter that is present – Example – volume, mass, amount of energy in the substance • Intensive properties – do not depend on the amount of matter that is present – Example – melting point, boiling point, density • Substance – matter that is uniform and has a definite composition – All samples of an identical substance have the identical physical and chemical properties Physical property – quality or condition of a substance that can be observed or measured without changing the substance’s composition Properties of Matter When a substance undergoes a physical change, its physical appearance changes. Ice melts: a solid is converted into a liquid. Physical changes DO NOT result in a change of composition. Examples of Physical Properties Color Odor Hardness Density Solubility Melting point, boiling point, freezing point Physical state – solid, liquid, gas • Page 40 Table 2.1 Physical properties of some substances States of matter • • • • Solid (s) Liquid (l) Gas (g) Plasma – we don’t deal with Classification of Matter States of Matter Matter can be a gas, a liquid, or a solid. Gases have no fixed shape or volume. Gases can be compressed to form liquids. Liquids have no shape, but they do have a volume. Solids are rigid and have a definite shape and volume. Gas and vapor not the same Gas – normally exists that way at room temperature Vapor – gas state of a substance that is normally a liquid or solid at room temperature Physical change • A change which alters a material without changing its composition • Cutting, grinding, melting, boiling, freezing, dissolving • Physical and Chemical Changes Mixtures Physical blend of two or more substances Composition can vary 2 types: Heterogeneous Homogeneous Heterogeneous Mixture Not uniform in composition Has 2 or more phases Phase – any part of a system with uniform composition and properties Dirt, salad, paper, rocky road ice cream Homogeneous Mixture Has a completely uniform composition All components are evenly distributed Consists of a single phase Called a SOLUTION Solution – what do you think of? • Can be gas, liquid, or solid!!!!! Separating mixtures Use PHYSICAL methods Magnet, sifting, Liquid mixtures – distillation Page 47 Organic distillation Distillation Substances Can be elements or compounds Element – definition Compound – 2 or more elements that have been CHEMICALLY combined. Can only be separated by CHEMICAL means • Sugar + heat carbon + water • Water + electric current hydrogen + oxygen Properties of compounds MUCH DIFFERENT THAN THE PROPERTIES OF THE ELEMENTS FROM WHICH THEY ARE COMPOSED!!!!! NaCl Matter substance element mixture compound heterogeneous homogeneous Flow chart – Pg. 50 Elements represented by symbols Compounds represented by formulas Pg. 52 Table 2.2 Chemical Change A change that produces matter with a different composition than the original matter Properties of Matter When a substance changes its composition, it undergoes a chemical change: When pure hydrogen and pure oxygen react completely, they form pure water. Is iron transforming into rust a physical or chemical change A. B. Physical Chemical Does the substance change composition or just change appearance? The color of sulfur is yellow.. A. B. Physical Chemical Does the substance change composition or just change appearance? Dynamite explodes to form a mixture of gases A. B. Physical Chemical Does the substance change composition or just change appearance? Aluminum melts at 933 K A. B. Physical Chemical Does the substance change composition or just change appearance? Plants use CO2 to make sugar A. B. Physical Chemical Does the substance change composition or just change appearance? Chemical Reactions One or more substances change into new substances REACTANT(S) PRODUCT(S) means “change into”, “produce”, “yields” Chemical Property • The ability of a substance to undergo chemical reactions and to form new substances • Rusting, burning, fermenting, exploding, rotting, decomposing • Iron and sulfur example Indications that a chemical reaction has occurred • Energy released or absorbed • Color change • Odor released • Production of a gas • Irreversibility • Production of light Law of Conservation of Mass • During any chemical reaction, the mass of the products is always equal to the mass of the reactants.