TYPES OF REACTIONS- Synthesis and decomposition

1. Level: Third Year High School TYPES OF REACTIONS- Synthesis and decomposition Charisma Jenny G. Mallari San Bartolome High School

2. OBJECTIVES At the end of the session, the students must be able to: • State the different types of chemical reactions. • Give examples of the different types of chemical reactions. Lesson Plan C. Mallari San Bartolome H.S. October 14, 2009

3. RECALL Draw your answer to the assigned query. • Left side: What happens to substances when there is a chemical change? • Middle: What happens to the atoms and molecules in a chemical change? • Right side: How do we classify these chemical changes? C. Mallari San Bartolome H.S. October 14, 2009

4. RECALL Left side: What happens to substances when there is a chemical change? Middle: What happens to the atoms and molecules in a chemical change? Right side: How do we classify these chemical changes? A new substance is formed C. Mallari San Bartolome H.S. October 14, 2009

5. MOTIVATION • What are the types of chemical reactions? C. Mallari San Bartolome H.S. October 14, 2009

6. Any Questions Let us perform today’s activity! Follow the assigned groupings. Activity Sheet C. Mallari San Bartolome H.S. October 14, 2009

7. Materials (PART I) • 1 to 4 cm of Mg ribbon • Crucible tongs • Alcohol lamp or Bunsen burner • Match C. Mallari San Bartolome H.S. October 14, 2009

8. Materials (PART II) • 9 Volt battery • 2 copper wires stripped at the ends • 250-mL beaker or a plastic soft drink bottle • 2pieces stainless steel electrodes or carbon rods (found inside the pencil) • 2 test tubes • Baking Soda NaHCO3 • Matchstick or splint C. Mallari San Bartolome H.S. October 14, 2009

9. PROCEDURE (Part I) Pick a piece of Mg ribbon using the crucible tongs. Burn the Mg ribbon. Do not look directly to the flame! It emits UV light. Record your observations. Remove the Mg ribbon when it is ignited. C. Mallari San Bartolome H.S. October 14, 2009

10. Procedure (PART II) Copper wire Carbon rod or stainless steel rod Beaker or plastic soft drink bottle Inverted test tube Half-fill the beaker with water. To increase the conductivity of water, use 10% NaHCO3. C. Mallari San Bartolome H.S. October 14, 2009

11. PROCEDURE (PART II) Slide the inverted test tube over one of the stainless steel electrodes. Fill a very small test tube with water Immerse in the NaHCO3 solution. Make sure that no bubbles appear in the test tube. Turn it upside down. C. Mallari San Bartolome H.S. October 14, 2009

12. PROCEDURE (PART II) Remove that test tube; keeping it inverted and dry, immediately test with a lighted match. Do it again for a second identical test tube. When one of the test tubes is filled with gas, disconnect the batteries. Connect the batteries. C. Mallari San Bartolome H.S. October 14, 2009

13. PROCEDURE (PART II) When the second test tube is totally filled with gas, repeat the test using a glowing matchstick. Record your observations. C. Mallari San Bartolome H.S. October 14, 2009

14. Data/Observations • PART II 4. What are the gases formed? ________________________________________ 5. What did you observe when we placed the lighted match into the mouth of the first test tube? ________________________________________ 6. What did you observe when we placed the glowing match into the mouth of the second test tube? ________________________________________ • PART I • What does the Mg react with? _______________________________________ 2. What is the balanced chemical equation that describes this reaction? _______________________________________ 3. Why do you think is this called a synthesis? _______________________________________ C. Mallari San Bartolome H.S. October 14, 2009

15. Data/observations • What is the balanced chemical equation that describes this reaction? ________________________________________ • Why do you think is this called a decomposition reaction? ________________________________________ C. Mallari San Bartolome H.S. October 14, 2009

16. DISCUSSION 1.What does the Mg react with? It reacts with oxygen gas in the air. 2. What is the balanced chemical equation for this reaction? 3. Why is this called a synthesis reaction? It is synthesis because 2 reactants combined to form one product. C. Mallari San Bartolome H.S. October 14, 2009

17. DISCUSSION C. Mallari San Bartolome H.S. October 14, 2009

18. DISCUSSION What did you observe when we placed the lighted match into the mouth of the first test tube? What did you observe when we placed the glowing match into the mouth of the second test tube? • Why do you think is this called a decomposition reaction? What are the gases formed? • What is the balanced chemical equation that describes this reaction? Hydrogen gas and Oxygen gas It is a decomposition reaction because a single reactant breaks down to form 2 products. H2(g) forms in the negative electrode. More bubbles are observed in this electrode than the positive electrode. When the gas was ignited, it produced a popping sound. When the glowing match/splint was inserted inside the test tube, the match/splint flamed again. 2 H2O(l) → 2H2(g) + O2(g) C. Mallari San Bartolome H.S. October 14, 2009

19. Thinking Pairs C. Mallari San Bartolome H.S. October 14, 2009

20. Conclusion The decomposition reaction is the opposite of a combination reaction. It involves breaking down one complex reactant (a compound) into 2 or more products (compounds). http://www.djusd.k12.ca.us/emerson/dphillips/documents/StudentebookChapter10.pdf • The synthesis or combination type of reaction involves adding together 2 or more reactants ( a compound or an element) to form one product (a compound). http://www.djusd.k12.ca.us/emerson/dphillips/documents/StudentebookChapter10.pdf C. Mallari San Bartolome H.S. October 14, 2009

21. ASSESSMENT Identify whether the reaction is a synthesis type or a decomposition type. ______ 1. Na2CO3 → Na2O + CO2 ______ 2. Pb + O2 → PbO2 ______ 3. 2 H2O → 2 H2 + O2 ______ 4. 8 Fe +S8 → 8 FeS ______ 5. 2 H2 + O2 → 2 H2O DECOMPOSITION SYNTHESIS DECOMPOSITION SYNTHESIS SYNTHESIS C. Mallari San Bartolome H.S. October 14, 2009

22. Application or valuing • These different reactions are seen everywhere • In industry • In our biological system • In the environment • We will discuss more of these next meeting! • Atoms are not created nor destroyed in a chemical reaction, but simply combine, separate, or rearrange. C. Mallari San Bartolome H.S. October 14, 2009

23. Application or valuing Why can’t we use the fire extinguisher to put out the flame of the burning Mg ribbon? Since magnesium burns in the presence of carbon dioxide, a CO2 fire extinguisher does not put out the flame from burning magnesium; a dry-chemical fire extinguisher must be used instead. C. Mallari San Bartolome H.S. October 14, 2009

24. ASSIGNMENT • Differentiate a combination or synthesis type of reaction from decomposition type of reaction. 2. What are the other types of chemical reactions aside from combination and decomposition? Give some example reactions. C. Mallari San Bartolome H.S. October 14, 2009

25. Works Cited • Burning Magnesium http://www.djusd.k12.ca.us/emerson/dphillips/documents/StudentebookChapter10.pdf • http://www.angelo.edu/faculty/kboudrea/demos/burning_magnesium/burning_magnesium.htm • http://www.youtube.com/watch?v=OTEX38bQ-2w&feature=related • Four types of chemical reactions http://www.youtube.com/watch?v=nVysOW0Lb8U C. Mallari San Bartolome H.S. October 14, 2009