Chemical Reactions

Physical Change Alters form and appearance of materials Melting, dissolving, freezing, separating Sublimation, deposition

Chemical Change A new substance is formed. Reactant(s) becomes Products A + B becomes C + D

Evidence for Chemical Change Precipitate - Solid comes out of a liquid Color Change Gas Production Change in Temperature Change in Properties - Soft dough to crust

Types of Chemical Reactions Synthesis - A + B becomes AB Decomposition - AB becomes A + B Replacement - AB + C becomes AC + B Double Replacement AB + CD becomes AC + BD

Getting it started Activation energy Every chemical reaction involves a change in energy. Exothermic - releases energy Endothermic - Absorbs energy

Rates of Chemical Reactions Concentration Surface Area Temperature Catalysts - Enzymes Inhibitors - Nitroglycerin - Dynamite

Chemical Equations Subscripts (next to and below atom symbol) - applies only to the element just to the left of the number. MgSO3 Coefficients (in front of molecule) - applies to all atoms in molecule. (Propane isomers) 2MgSO3 (CH3)3CH or C4H10

Balancing equations Conservation of Mass - Total mass of reactants has to equal the total mass of the products