Chemical Reactions Chemical Changes Balancing Chemical Equations 1

Physical Properties color melting point boiling point electrical conductivity specific heat density state (solid, liquid, or gas) 2

Physical Change Changes in physical properties melting freezing boiling condensation Sublimation Example: Ice, rain, and steam are all water so this change in state is only a physical change. 3

Chemical Change Atoms are rearranged to form one or more different substances Old bonds are broken; new bonds form Examples: Fe and O 2 form rust (Fe 2 O 3 ) Ag and S form tarnish (Ag 2 S) 4

Quick quiz 1 Classify each of the following as a 1) physical change or 2) chemical change A. ____ a burning candle B. ____ melting ice C. ____ toasting a marshmallow D. ____ cutting a pizza E. ____ polishing silver 5

Quiz 1 check Classify each of the following as a 1) physical change or 2) chemical change A. __2__ a burning candle B. __1_ melting ice C. __2__ toasting a marshmallow D. __1__ cutting a pizza E. __2__ polishing silver 6

Chemical Reaction A process in which at least one new substance is produced as a result of chemical change. 7

A Chemical Reaction Reactants Products 8

Quick Quiz 2 A. How did the rust equation show that a new substance had formed? B. How did the yellow and green reactants combine? C. Did all the reactants form product? Why or why not? 9

Quiz 2 Check A. How did the rust equation show that a new substance had formed? The formulas of the reactants are different than the formulas of the products. B. How did the yellow and green reactants combine? 1 yellow combined with 1 green. C. Did all the reactants form product? Why or why not? No. There were more yellow reactants than green. 10

Writing a Chemical Equation Chemical symbols give a “before-and-after” picture of a chemical reaction Reactants Products MgO + C CO + Mg magnesium oxide to form carbon monoxide reacts with carbon and magnesium 11

Quick quiz 3 1.What side of the equation can you find the Reactants? 2. What side are the products on? 3. What symbol is used to show where the energy in the reaction is (yield)? 12

Quiz 3 Check 1.What side of the equation can you find the Reactants? LEFT SIDE 2. What side are the products on? RIGHT SIDE 3. What symbol is used to show where the energy in the reaction is (yield)? AN ARROW 13

Reading A Chemical Equation 4 NH O 2 4 NO + 6 H 2 O Four molecules of NH 3 react with five molecules O 2 to produce four molecules NO and six molecules of H 2 O or Four moles NH 3 react with 5 moles O 2 to produce four moles NO and six moles H 2 O 14

A Balanced Chemical Equation CONSERVATION OF MASS!!!!!! Same numbers of each type of atom on each side of the equation Al + S Al 2 S 3 Not Balanced 2Al + 3S Al 2 S 3 Balanced 15

CONSERVATION OF MASS!!!!!!!! H 2 + Cl 2 2 HCl ++ Total atoms=Total atoms 2 H, 2 Cl2H, 2 Cl Total Mass =Total Mass 2(1.0) + 2(35.5) 2(36.5) 73.0 g=73.0 g 16

Law of Conservation of Mass In any ordinary chemical reaction, matter is not created nor destroyed 17

Balance Equations with Coefficients Coefficients in front of formulas balance each type of atom 4NH 3 + 5O 2 4NO + 6H 2 O 4 N = 4 N 12 H=12 H 10 O=10 O 18

Steps in Balancing An Equation Fe 3 O 4 + H 2 Fe + H 2 O Fe: Fe 3 O 4 + H 2 3 Fe + H 2 O O:Fe 3 O 4 + H 2 3 Fe + 4 H 2 O H: Fe 3 O H 2 3 Fe + 4 H 2 O 19

Quick quiz 4 Fe 3 O H 2 3 Fe + 4 H 2 O A. Number of H atoms in 4 H 2 O 1) 22) 43) 8 B. Number of O atoms in 4 H 2 O 1) 22) 43) 8 C. Number of Fe atoms in Fe 3 O 4 1) 12) 33) 4 20

Quiz check 4 Fe 3 O H 2 3 Fe + 4 H 2 O A. Number of H atoms in 4 H 2 O 3) 8 B. Number of O atoms in 4 H 2 O 2) 4 C. Number of Fe atoms in Fe 3 O 4 2) 3 21

Quick quiz 5 Balance each equation. The coefficients for each equation are read from left to right A. Mg + N 2 Mg 3 N 2 1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1 B. Al + Cl 2 AlCl 3 1) 3, 3, 22) 1, 3, 13) 2, 3, 2 22

Quick quiz 5 Continued!!! C. Fe 2 O 3 + C Fe + CO 2 1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3 D. Al + FeO Fe + Al 2 O 3 1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1 E. Al + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2 1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3 23

QUIZ 5 Check A. 3 Mg +N 2 Mg 3 N 2 B. 2 Al + 3 Cl 2 2 AlCl 3 C. 2 Fe 2 O C 4 Fe + 3 CO 2 D. 2 Al + 3 FeO 3 Fe + Al 2 O 3 E. 2 Al + 3 H 2 SO 4 Al 2 (SO 4 ) H 2 24