I. Chemical Changes in Matter

An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron. Oxidation and Reduction Reactions (REDOX Rxns) video clip Redox Rxns: oxidation-reduction rxns transfer es LEO says GER

Oxidation: Reduction: gain e lose e charge charge 0 0 0 0 0 0 0 00 0 0 REDOX:

transfer e 00 2 +3 2 2 +3 +3 2 4 Fe(s) + 3 O2(g) 2 Fe2O3(s) Metals: tend to be oxidized (lose e) Nonmetals: tend to be reduced (gain e) magnesium 0 0 0

0 magnesium sulfide sulfur 0 0 0 0 +2 2 +22 +2 2

Mg(s) + S(s) MgS(s) Metals: tend to be oxidized (lose e) Nonmetals: tend to be reduced (gain e) LEO says GER 0 0 +2 2 -4 +1

0 +4 -2 +1 -2 CH4(g) + O2(g) CO2(g) + H2O(g) Oxidized? (charge ) Reduced? (charge ) +1 -1 +2 -1 +1 -1 +2 -1 2NaF(aq) + CaCl2(aq) 2NaCl(aq) + CaF2(s)

Oxidized? (charge ) Reduced? (charge ) NOT REDOX because NO charges changed (NO e loss or gain) Redox in Living Systems Photosynthesis O2 is oxidized to O20 +4 2 +1 2 0

+1 2 0 6CO2 + 6H2O C6H12O6 + 6O2 C+4 is reduced to C0 Redox in Living Systems Cellular Respiration C0 is oxidized to C+4 0 +1 2

0 +4 2 +1 2 C6H12O6 + 6O2 6CO2 + 6H2O O0 is reduced to O2 Quick Quiz! 1. During oxidation, an element _______ electrons. During reduction, an element ________ electrons. A. B. C. D.

gains, loses loses, gains gains, donates gains, accepts Quick Quiz. 2. Which element is reduced in the following chemical reaction? +3 2 +2 2 0 +4 2 Fe2O3 + 3 CO 2 Fe + 3 CO2

A. B. C. D. O Fe C none (not redox)