Ch 6.1 Chemical Reactions

Objectives For this Chapter Understand parts to a chemical equation (reactants, products, yeild sign, double arrow) Conservation of matter is expressed through balancing chemical equations Describe difference between endothermic and exothermic reactions

Review from Ch 2 Chemical Change: Atoms in the reactants are rearranged to form one or more different substances Old bonds are broken; new bonds form Ex) Fe and O2 form rust (Fe2O3) Ag and S form tarnish (Ag2S)

Basic Chemical Equation -Objective ______ + _______ __________ Reactants Products

Chemical Reaction A process in which at least one new substance is produced as a result of a chemical change

Signs of a chemical reaction In nature: grow, ripen, decay, burn In the lab: bubbles, change in color, precipitate forms, light and heat produced

1. The hydrogen peroxide oxidizes the phenyl oxalate ester, resulting in a chemical called phenol and an unstable peroxyacid ester. 2. The unstable peroxyacid ester decomposes, resulting in additional phenol and a cyclic peroxy compound. 3. The cyclic peroxy compound decomposes to carbon dioxide. 4. This decomposition releases energy to the dye. 5. The electrons in the dye atoms jump to a higher level, then fall back down, releasing energy in the form of light.

Energy and Reactions Energy needed to break bonds and form new compounds Energy is released when new compounds are formed Energy is conserved. Total energy before reaction = total energy of products

Objective Exothermic reaction - reaction that gives off heat energy – feels hot Endothermic reaction - reaction that absorbs heat energy – feels cold