Physical Science Unit 7 Study Guide - Answers

Name __________________ Date _________ Physical Science Unit 7 Study Guide: Chemical Reactions • Review: Chemical vs. Physical Properties and Changes 1. List 5 examples of physical properties. Temperature Color Mass Volume 2. List 5 examples of physical changes. Freezing Melting Evaporating

Size Density Solubility Shape Breaking Separating Mixing

3. List 5 different types of evidence that a chemical change has occurred and list what types of observations you would make for each one. Release of a gas Change in color Formation of a precipitate Presence of an odor Change in energy 4. What is a precipitate? Is the solid that forms when you mix two solutions 5. Which of the following is a physical change? a. Formation of a silver sulfide when silver reacts with sulfur in the air b. Burning methane gas, producing water and carbon dioxide c. Condensation of water vapor on the outside of a cold can of soda d. Vinegar and baking soda combining and forming a salt and water • Distinguish Between Chemical and Physical Changes 6. When does a chemical change occur? When there is a rearrangement of atoms. A new substance is produced 7. What is the difference between a chemical change and a physical change? A chemical change occurs when you have a new substance. A physical change occurs when you have the same substance as you started with 8. What is the difference between a color change as a chemical change and a physical change? When there is a color change that is a physical change it is just mixing. When it is a result of a chemical change it is because a new substance is produced. • The Basics of Chemical Reactions 9. In the equation: 2 H2 + O2  2 H2O + energy what is the 2 in front of H2 called? What does it mean? It is the coefficient. It means there are two H2 10. In the equation: 2 H2 + O2  2 H2O + energy what are the reactants? What are the products? Reactants - H2 + O2 Products- H2O

Name __________________ Date _________ 11. In the equation: 2 H2 + O2  2 H2O + energy is this reaction endothermic or exothermic? How do you know? This is exothermic because it is producing energy • Balancing Equations • Balancing Equations….More Help 12. How many atoms of each element are in the following molecules? a. H3PO4 H=3 P=1 O=4 b. MgCl2 Mg = 1 Cl = 2 c. Pb(NO3)2 Pb = 1 N=2 O=6 d. 3Mg(CO3)2 Mg = 3 C = 2x1=2; 2x3= 6 O = 2 x 3 =6; 6 x 3 = 18 e. 4NH3 N=4 H = 4 x 3 = 12 13. Are the following equations balanced or unbalanced? a. MnO2 + HCl  H2O + MnCl2 + Cl2 Unbalanced (2 O  1 O) b. 2 NH3 + H2SO4  (NH4)2SO4 Balanced because they all equal c. 2 Ca + 6 HCl  2 CaCl3 + 4H2 Unbalanced H=6  H=8 d. 3 FeO + 2 Al  Al2O3 + 3 Fe Balanced because they are all equal e. 2 NaOH + 2 H2SO4  Na2SO4 + 2 H2O Unbalanced ( 6 H  4 H) f. 3 Al + 3 AgC2H3O2  Al(C2H3O2)3 + 3 Ag

Name __________________ Date _________ Unbalanced (3 Al  1 Al) g. I2 + 5 Cl2 + 6 H2O  2 HIO3 + 10 HCl Balanced they are all equal I=2; Cl=10; H=12; O=6 14. Balance the following chemical reactions: a. __2__ K + ____ Cl2  __2__ KCl K=1x2 K=1 x2 Cl=2 Cl=1 x 2 b. ____ N2 + __3__ F2  __2__ NF3 N= 2 N=1x2=2 F= 2x3=6 F=3x2=6 c. ____ CH4 + __2__ O2  ____ CO2 + __2__ H2O1 C=1 C=1 H=4 H=2x2=4 O=2x2=4 O=2+1x2=4 d. ____ CF4 + __2__ Br2  ____ CBr4 + __2__ F2 C=1 C=1 F=4 F=2x2=4 Br=2 x2=4 Br=4 e. __2__ Al + _6__ HCl  __3__ H2 + __2__ AlCl3 Al = 1x2 Al = 1x2 H = 1x6 H = 2x3=6 Cl = 1x6 Cl= 3x2=6

f. __2__ AgNO3 + ____ Cu  ____ Cu(NO3)2 + ___2_ Ag Ag=1x2 Ag=1x2 N=1x2 N=2 O=3x2=6 O=6 Cu=1 Cu=1 g. __2__ Na3PO4 + __3__ CaCl2  __6__ NaCl + ____ Ca3(PO4)2 Na=3x2 Na=1x3=3x2=6 P=1x2 P=2 O=4x2=8 O=8 Ca=1x3 Ca=3 Cl =2x3=6 Cl=1x3=3x2=6

Name __________________ Date _________ • The 5 Types of Chemical Reactions 15. Are the following reactions synthesis, decomposition, single replacement, double replacement, or combustion? a. CuSO4 + Na3PO4  CuPO4 + Na3SO4 Double replacement b. Fe + CuCl2  FeCl2 + Cu Single replacement c. 4 Al + 3 O2  2 Al2O3 Synthesis d. 2 C5H10 + 15 O2  10 CO2 + 10 H2O Combustion e. 2 Al + 3 CuSO4  3 Cu + Al2(SO4)3 Single Replacement f. 2 SnO + 2 C  2 SnC + O2 Single replacement g. Pb(NO3)2 + H2SO4  H2(NO3)2 + PbSO4 Double replacement h. CaCO3  CO2 + CaO Decomposition