Name: Date Due: Chemical Reactions. Physical Science Chapter 12

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1 Name: Date Due: Chemical Reactions Physical Science Chapter 12

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3 What are Chemical Reactions? 1. Define the following terms: a. chemical reaction= a. reactants= b. products= c. chemical equation= d. law of conservation of mass= e. mole= f. molar mass= 2. What does a useful description of a chemical reaction tell you? 3. Do chemical reactants and products contain the same atoms in a chemical reaction? 4. How do the atoms form different combinations in the products from the reactants? 5. How are chemical reactions represented? 6. What do the arrows show? 3

4 7. Why must a chemical equation be balanced? 8. Write a balanced for each of the following. Cu+ O2 CuO HCl + NaOH NaCl + H 2 O C + S 8 CS 2 Na + O 2 Na 2 O 2 N 2 + O 2 N 2 O 5 9. Which of the following chemical equations is balanced? a. Zn+HCl ZnCl 2 +H 2 b. 2Zn+2HCl ZnCl 2 +H 2 c. 2Zn+HCl ZnCl 2 +H 2 d. Zn+2HCl ZnCl 2 +H How do you determine molar mass for an element? 11. How do you determine molar mass for a compound? 12. How do you convert moles into mass? 13. Explain how a balanced chemical equation shows that mass is conserved. 4

5 14. What is a coefficient? 15. Why must chemical equations be balanced? 16. The following equation describes how sodium and chlorine react to produce sodium chloride. 2Na + Cl 2 2NaCl Is the equation balanced? Explain your answer. 17. Write a balanced chemical equation for the formation of magnesium oxide, MgO, from magnesium and oxygen. 18. As a candle burns, its mass decreases. However, mass is conserved in this reaction. Explain this observation. 5

6 Types of Reactions 19. Define the following terms: a. Synthesis reaction= b. Decomposition reaction= c. Single replacement reaction= d. Double replacement reaction= e. Combustion= f. Oxidation-reduction reaction= g. oxidation= h. reduction = i. chemical energy= j. exothermic reaction= k. endothermic reaction= l. activation energy= m. law of conservation of energy= 6

7 20. Identify these reactions as synthesis, decomposition, single replacement, double replacement, or combustion. Pb(NO3)2 + 2HCl 2C2H6 + 7O2 PbCl2 + 2HNO3 4CO2 + 6H2O Ca + 2HCl 2SO2 + O2 CaCO3 CaCl2 + H2 2 SO3 CaO + CO2 21. Why are oxidation and reduction always together? 22. Contrast exothermic and endothermic chemical reactions. 23. Give an example when you have used activation energy to start a chemical reaction. 24. Why is the amount of energy the same before and after a chemical reaction? 7

8 Covalent Bonds 25. Define the following terms: a. radioactivity= b. radiation= c. radioactive isotope= d. nuclear radiation= e. alpha particle= f. beta particle= g. gamma ray= h. background radiation= i. half-life= j. radioactive dating= k. weak nuclear force= l. strong nuclear force= m. nuclear fission= n. uncontrolled nuclear fission= 8

9 o. nuclear fusion= 26. Why are some nuclei unstable? 27. List the types of nuclear radiation from least penetrating to most penetrating. 28. What contributes to background radiation? 29. How can radiation damage cells? 30. What devices are used to detect nuclear radiation? 31. How can radioactivity be useful? 32. Why do some radioisotopes decay at a faster rate? 33. Which radioactive isotope would be used to date a rock from about 10,000 years ago? 34. What holds the nucleus together? 35. What changes in a nuclear reaction? 9

10 36. What is an advantage of nuclear fission? 37. What are advantages and disadvantages to nuclear fusion? 38. Complete the Venn diagram on nuclear fission and nuclear fusion. Nuclear Fission Nuclear Fusion 10

11 Modeling Radioactive Decay Lab Background Information: Radiometric dating is the most commonly used absolute dating technique for rocks older than Pleistocene. Many elements have one or more isotopes that are radioactive. Some radioactive isotopes, for example 235 U and 238 U, were incorporated into Earth during the formation of the solar system. Other radioactive isotopes, for example 14 C, are produced continually in Earth s atmosphere or on the surface by interactions with cosmic rays. Radioactive isotopes all spontaneously decay to isotopes of daughter elements. Eventually, all isotopes decay to a nonradioactive stable isotope of a daughter element. Although the decay events occur at random, we can statistically determine what percentage of the atoms of a given isotopes will decay within a specified period of time. Each radioactive isotope decays at a different rate expressed as half-life. The half-life of an isotope is defined as the length of time required for ½ of the atoms of that isotope to decay to their daughter isotopes. The half-lives for different isotopes range from nanoseconds to billions of years. Commonly Used Isotopes Radioactive Isotope Half-Life Stable Daughter Isotope Rubidium Billion Years Strontium-87 Uranium Billion Years Lead-206 Potassium Billion Years Argon-40 Uranium Million Years Lead-207 Carbon Years Nitrogen-14 Materials: 50 pennies, cup, and graph paper Procedure: 1. Place all the pennies into the cup and shake to mix them well. 2. Spread the pennies onto the table without altering the heads/tail ratio. 3. Count the number of heads radioactive element. Tails represents stable daughter isotopes. Record in your data table. 4. Put only the head back into the cup and shake. 5. Repeat steps 2-4 until you do not have any more heads. 6. Plot your results on the graph paper. 11

Data: Trial # 0 1 2 3 4 5 6 7 8 9 10 # of Heads 50 Percentage 100 Ideal % 100 50 25 12.5 6.25 3.13 1.56 0.78 0.39 0.20 0.

12 Data: Trial # # of Heads 50 Percentage 100 Ideal % Percentage = # of Heads/Total # of Pennies % Half-Life Data = Your Percentage = Ideal Percentage Trial Number 12

13 Analysis: 1. How does the ideal data differ from your group s data? 2. Explain how each trial represents one half-life of our radioactive isotope. 3. What are assumptions of using half-life to determine age? (Hint: Why is using half-life not always accurate?) 4. How can the percentages of parent material be used to determine radiometric dates? 13

HIGH SCHOOL SCIENCE. Physical Science 12: Chemical Reactions

HIGH SCHOOL SCIENCE. Physical Science 12: Chemical Reactions HIGH SCHOOL SCIENCE Physical Science 12: Chemical Reactions WILLMAR PUBLIC SCHOOL 2013-2014 EDITION CHAPTER 12 Chemical Reactions In this chapter you will: 1. Interpret and balance chemical equations.