Chemical Reactions
SC Standards PS-4.6 Distinguish between chemical changes (including the formation of gas or reactivity with acids) and physical changes (including changes in size, shape, color, and/ or phase). PS-4.7 Summarize characteristics of balanced chemical equations (including conservation of mass and changes in energy in the form of heat-that is, exothermic or endothermic reactions). PS-4.8 Summarize evidence (including the evolution of gas; the formation of a precipitate; and/ or changes in temperature, color, and/ or odor) that a chemical reaction has occurred. PS-4.9 Apply a procedure to balance equations for a simple synthesis or decomposition reaction. PS-4.10 Recognize simple chemical equations (including single replacement and double replacement) as being balanced or not balanced. PS-4.11 Explain the effects of temperature, concentration, surface area, and the presence of a catalyst on reaction rates.
Signs of a Chemical Reaction Production of light Formation of a gas Formation of a precipitate Color change Change in temperature
Law of Conservation of Mass mass is neither created nor destroyed in a chemical reaction 4 H 2 O 4 H 2 O 4 g32 g 36 g total mass stays the same atoms can only rearrange
Chemical Equations A+B C+D REACTANTS PRODUCTS
Chemical Equations
Types of Chemical Reactions
Synthesis the combination of 2 or more substances to form a compound only one product A + B AB
Synthesis H 2 (g) + Cl 2 (g) 2 HCl(g)
Decomposition a compound breaks down into 2 or more simpler substances only one reactant AB A + B
Decomposition 2 H 2 O(l) 2 H 2 (g) + O 2 (g)
Single Replacement one element replaces another in a compound metal replaces metal (+) nonmetal replaces nonmetal (-) A + BC AC + B
Single Replacement Cu(s) + 2AgNO 3 (aq) Cu(NO 3 ) 2 (aq) + 2Ag(s)
AB + CD AD + CB Double Replacement ions in two compounds “change partners” cation of one compound combines with anion of the other
Double Replacement Pb(NO 3 ) 2 (aq) + K 2 CrO 4 (aq) PbCrO 4 (s) + 2KNO 3 (aq)
Double Replacement Reaction Lab