General Chemistry Zumdahl Chapter 7 Notes Chemical Reactions Week of 1/26/15, Expected test date, Tuesday 2/3/15 Standard: HS-PS1-7 Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Introduction Where do we see chemical reactions?(1) Everywhere! Cars driving, hair growing, clothes being made, etc…

7.1 Evidence for a Chemical Reaction p. 193 of book Most chemical reactions give a visual signal when they occur. What are some examples of these visual changes?(2) Color change Precipitate (solid) forms Gas is formed (bubbles) A flame forms

7.2 Chemical Equations, p. 195 Define Chemical reaction(3): Atoms of different compounds are rearranged forming new compounds Chemical equation(4): A visual representation of a chemical reaction Reactant(5): Chemicals before the reaction Products(6): Chemicals after the reaction

7.2 Chemical Equations What are the abbreviations for Solid (7): (s) Liquid (8): (l) Gas (9): (g) Dissolved in water or aqueous (10): (aq)

7.3 Balancing Chemical Equations, p. 200 It is important to understand that in a chemical reaction atoms are neither created nor destroyed. There are the same amount of each atom on the reactant side as there are on the product side.

7.3 Balancing Chemical Equations The burning of methane gas produces carbon dioxide and water CH4(g) + O2(g)  CO2(g) + H2O(l) What is wrong with this?(11) Not balanced! CH4(g) + 2O2(g)  CO2(g) + 2H2O(l)

7.3 Balancing Chemical Equations The chemical formation of water H2(g) + O2(g)  H2O(l) What is wrong with this?(12) Not balanced 2H2(g) + O2(g)  2 H2O(l) Define coefficient(13): The number of compounds that is needed to make equation balanced.

7.3 Balancing Chemical Equations Balance (14) C2H5OH(l) + O2(g)  CO2(g) + H2O(l) C2H5OH(l) + 3O2(g)  2CO2(g) + 3H2O(l) N2(g)+H2(g) NH3(g) N2(g)+3H2(g)2 NH3(g) O2(g)  O3(g) 3O2(g)  2O3(g)