OBJECTIVE10/11/13 TLW, with 100% participation, distinguish between physical and chemical changes, discern indicators of a chemical reaction, analyze components of a chemical equation, determine whether the equations comply with the Law of Conservation of Mass by being balanced.

Warmup10/11/13 Complete the table below: SUBSTAN CE NUMBER OF MOLECUL ES ELEMENT S (NAME) NUMBER OF ATOMS OF EACH ELEMENT 3CO 2 3CARBON, OXYGEN C=3, O=6 18H 2 SO 4 6C 6 H 12 O 6

Warmup10/11/13 SUBSTANCENUMBER OF MOLECULES ( COEFFICIENT) ELEMENTS (SYMBOLS) NUMBER OF ATOMS OF EACH ELEMENT (Coefficient x subscript) 3CO 2 3 CARBON, OXYGEN C=3, O=6 18H 2 SO 4 18 HYDROGEN, SULFUR, OXYGEN H= 36, S=18, O=72 6C 6 H 12 O 6 6 CARBON, HYDROGEN, OXYGEN C=36, H=72, O=36

Physical vs. Chemical Changes Physical Changes A substance changes but doesn’t become a new substance. Ex. Change in state (solid, liquid, or gas) Glass braking Piece of wood used to make a bat Dissolving sugar in water Chemical Changes Bonds are made or broken to make a new substance Ex. Burning substances Electrolysis Rusting Tarnishing

What Happens as a Result of a Chemical Change? In the process of an object undergoing a chemical change, a chemical reaction is occurring as new substances are being formed.

Indicators of chemical reactions Formation of a gas (bubbles) Emission of light or heat Formation of a precipitate Color change Formation of a gas (odor)

Chemical Equations: Represent a chemical reaction & consist mainly of two parts. Reactants Starting material Products New substance

Chemical Equations Tells us the number of molecules (coefficients) and atoms (subscripts) involved Must be balanced to support the Law of Conservation of Mass

Parts of a Chemical Equation Chemical formula Chemical symbol coefficient subscript yields reactants products

Balanced? 3H 2 SO 4 + 2FeFe 2 (SO 4 ) 3 + 3H 2 ReactantsProducts H = 6 S = 3 O = 12 Fe = 2 H = 6 S = 3 O = 12 Fe = 2

All chemical reactions are accompanied by a change in energy. Reaction Energy Exothermic - reactions that release energy to their surroundings (usually in the form of heat) Endothermic - reactions that need to absorb heat from their surroundings to proceed.

Types of Reactions Synthesis (combination) Decomposition Combustion Single Replacement Double Replacement

Synthesis Reactions 2 elements, or compounds combine to make one compound. A + B  AB Na + Cl 2  NaCl

Decomposition Reactions decompose = fall apart one compound (reactant) falls apart into two or more elements or compounds. Usually requires energy AB  A + B CaCO 3 CaO + CO 2

Single Replacement Also referred to as single displacement One element replaces another Reactants must be an element and a compound. Products will be a different element and a different compound. A + BC  AC + B 2Na + SrCl 2  Sr + 2NaCl F 2 + LiCl  LiF + Cl 2

Double Replacement Two things replace each other. Reactants must be two ionic compounds or acids. AB + CD  AD + CB AgNO 3 + NaCl  AgCl + NaNO 3 ZnS + 2HCl  ZnCl + H 2 S

Combustion A reaction in which a compound (often carbon) reacts with oxygen CH 4 + O 2  CO 2 + H 2 O C 3 H 8 + O 2  CO 2 + H 2 O C 6 H 12 O 6 + O 2  CO 2 + H 2 O

Examples Synthesis Decomposition Single replacement Double replacement H 2 + O 2  H 2 O  AgNO 3 + NaCl  Zn + H 2 SO 4  HgO  KBr +Cl 2  Mg(OH) 2 + H 2 SO 3 