1. Ms. Ashley Lardizabal Chemistry DISCOVERY SCHOOL

2.   Define physical change and list several common physical changes.  Define chemical change and list several indications that a chemical change has taken place.  Apply the law of conservation of mass to chemical reactions. OBJECTIVES

3.   Physical change  Chemical change  Law of conservation of mass VOCABULARY

4.   A substance often undergoes changes that result in a dramatically different appearance but leave the substance unchanged.  EXAMPLE: Crumpling aluminum foil  PHYSICAL CHANGES are changes that alter a substance without changing its composition.  EXAMPLES:  Cutting a sheet of paper  Breaking a crystal  Include verbs: bend, grind, crumple, spit, & crush PHYSICAL CHANGES

5.   The state of matter depends on the temperature and pressure of the surroundings  As temperature and pressure change, most substances undergo a change from one state (or phase) to another  EXAMPLE: Water  0°C  solid state AKA ice  Above 0°C  melts and becomes liquid water  100°C  water begins to boil as liquid water turns to steam PHYSICAL CHANGES

6.   Terms that indicate phase change:  Boil  Freeze  Condense  Vaporize  Melt  The temperature and pressure at which a substance undergoes a phase change are important physical properties  Melting point  Boiling point PHYSICAL CHANGES

7.   Chemical properties relate to the ability of a substance to combine with or change into one or more substances  A process that involves one or more substances changing into new substances is called a CHEMICAL CHANGE  AKA as a CHEMICAL REACTION  The new substances formed in the reaction have different compositions and different properties from the substances present before the reaction. CHEMICAL CHANGE

8.   EXAMPLE:  Grapes  Wine  Iron  Rust  Terms that indicate a chemical reaction:  Explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot CHEMICAL CHANGE

9.   Formation of a gas or solid  Color changes  Energy change  Change in smell or production of odor Evidence of a Chemical Reaction

10.   In the 18 th century, scientist began to use quantitative tools to monitor chemical changes  The analytical balance  Capable of measuring very small changes in mass  By carefully measuring mass before and after many chemical reactions, it was observed that, although chemical changes occurred, the total mass involved in the reaction remained constant. Conservation of Mass

11.   The constancy of mass in chemical reactions was observed so often that scientist assumed the phenomenon must be true for all reactions.  LAW OF CONSERVATION OF MASS  States that mass is neither created nor destroyed during a chemical reaction – it is converved  Mass reactants = Mass products Conservation of Mass

12.   Antoine Lavoisier (1743-1794)  First to use analytical balance  Studied the thermal decomposition of mercury(II) oxide, known as calx of mercury  Mercury(II) oxide is a powdery red solid  When it is heated, the red solid reacts to form the silvery liquid mercury and colorless oxygen gas  The color change and production of gas are indicators of a chemical reaction. Conservation of Mass

13.   Fundamental concept of chemistry  When the reaction is performed in a closed container, the oxygen gas cannot escape and the mass before and after the reaction can be measured  The masses will be the same. Conservation of Mass

14.   In an experiment, 10.00 g of red mercury(II) oxide powder is placed in an open flask and heated until it is converted to liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction? EXAMPLE: Law of Conservation of Mass

15.   Practice problems  #1-4  Assessment Questions  #1-5 HOMEWORK