Chapter 4 Properties of Matter Objectives:  Distinguish between chemical and physical properties (4.1)  Distinguish between chemical and physical changes ( )  Understand Conservation of Mass (4.4)  Define and understand energy and it’s relation to chemistry ( )

Properties of Substances  “personality traits” of substances  Physical Properties:  Inherent characteristics  Determined without altering composition  Chemical Properties  Ability of a substance to form new substances

Physical Properties  Color  Taste  Odor  State of matter (solid, liquid, gas)  Density  Melting point  Boiling point

Chemical Properties  Ability to react with other substances  Decompose  Elements it will react with  Types of reactions possible

Physical Changes  Changes in physical properties  Color change  Change in density  Change in size or shape  No new substances form  Composition is not changed  Ice melting into water (both still H 2 O)

Chemical Changes  New substances formed with DIFFERENT properties and composition  Electrolysis of water into hydrogen and oxygen  Burning of paper  Cannot get original substances back without chemical reaction

Chemical Changes  Usually shown with chemical equation  Words or symbols (more later…)  Reactants  What goes into reaction  Written on the left of the arrow  Products  What comes out of a reaction  Written to right of arrow

Chemical Changes  Example: Water hydrogen + oxygen 2H 2 O 2H 2 + O 2

Physical or Chemical Change?  Rusting of iron  Boiling of water  Burning of sulfur  Combustion of gasoline  Digesting food  Heating of glass  Lighting a candle Chemical Physical

Conservation of Mass  Law of Conservation of Mass:  No change is observed in the total mass of the substances involved in a chemical change  Mass of reactants = mass of products  Water hydrogen + oxygen  g11.2 g88.8 g  Reactants = 100.0g  Products = g

Energy  Definition: the capacity of matter to do work  Potential Energy: stored energy  Kinetic Energy: energy of motion  One form of energy can be transformed into another form…  Electric generator (mechanical to electrical energy)  Solar panels  All chemical changes absorb or release energy!!!

Units to Measure Energy  SI unit: joule (J)  Calorie (cal) or kilocalorie (kcal or Cal)  J = 1 cal  Quantity required to raise 1 gram of water by 1 0 C  Heat vs. Temperature  Temperature…what you measure with a thermometer  Heat…energy it takes to raise something to a particular temperature

Units to Measure Energy  Specific heat  Quantity of heat required to change the temperature of 1 g of that substance by 1 o C  Heat = t (specific heat of substance)(mass of substance) 8.37 x 10 3 J  How much heat is needed to raise temperature of 200. g of water by C?  (200.0g)(4.184 J/g 0 C)( C) =

Law of Conservation of Energy  Energy can be neither created nor destroyed, although it can be transformed from one form to another