CARBON MONOXIDE: LESSON ONE What is Complete & Incomplete Combustion? LESSON SUMMARY Grade Level: 9 – 12 This lesson introduces students to the concepts of complete and incomplete Subject(s) Addressed: combustion, and ultimately the production of carbon monoxide during Science, Chemistry, Math incomplete combustion. In Lab 1 “The Life of a Candle,” students examine the process of combustion by subjecting a burning candle to differing conditions. Class Time: 1-4 Periods Additionally, students will determine the reactants and products involved in Inquiry Category: Guided complete and incomplete combustion, and the role each of these plays in combustion. Finally, students will conclude that incomplete combustion can result in the production of carbon monoxide. “What is Complete and Incomplete Combustion” also serves as an introduction to Lesson Two: What are the Health Effects of Carbon Monoxide? CORE UNDERSTANDING/OBJECTIVES By the end of this lesson, students will have a basic understanding of the Combustion Triangle, complete and incomplete combustion, and the reactants/products of combustion. Students will be introduced to the importance of carbon monoxide as a dangerous environmental pollutant that is often a by-product of combustion. For specific learning objectives and standards addressed, see pages 32 and 33. MATERIALS/INCORPORATION OF TECHNOLOGY The Life of a Candle? Wooden splint Taper candle & holder Food coloring Matches or lighter Tissue White paper or cardstock Tongs Flashlight Microscope slides 3 clear glass jars with lids (~200 mL) Lab goggles Limewater solution Detecting Carbon Monoxide Flexible straws Lascar CO Detector Protocol SUGGESTED READINGS The origin, fate, and health effects of combustion by-products: a research framework. http://1.usa.gov/1cQyfRK What Are the Different Types of Combustion Products? http://bit.ly/1jAF5ws INDIAN EDUCATION FOR ALL Fire was a critical resource for the early American Indians and had functions beyond just warmth and cooking. According to Henry T. Lewis, early Indians used fire to aid in hunting, crop management, to improve growth and yields of CO Lesson 1 vegetation, and for safety reasons including fireproofing areas of settlement. There were many other uses for fire as well, ranging from insect collection to warfare signaling. ENGAGE Begin the lesson by lighting a candle in front of the class. Let it burn for a few minutes until there is consistent flame. Instruct the students to take out a piece of paper and record as many observations as they can about the burning candle. This may be a good place to discuss the differences between observation and inferences. Initiate a class discussion concerning student observations. Then, have the students number 1 through 5 below their burning candle observations. Ask the following questions allowing students time to record their answers: 1) How does a candle burn? and 2) How does a candle continuously produce a flame? After students have recorded their answers, have them review their answers to the questions in small groups. Have each group write their answers on the board and review the answers as a class. Have students return to their individual desks. Next, light a Coleman lantern or a Bunsen burner near the candle. Ask the students to record their answers to the following questions: 3) How does a Coleman lantern/Bunsen burner burn?, 4) If the lantern/Bunsen has no fuel, will it still burn? Please explain. After students answer these questions, ask them to revisit their answers about the candle. For question #5, ask students to answer question #1 again and revise their original answer if needed, “How does a candle burn?” Collect the students’ answers and let them know you will revisit them at the end of the lesson. VOCABULARY Copies of blank student vocabulary banks (see page 4) can be distributed for completion as either a classroom or homework assignment. EXPLORE Distribute Lab 1: “The Life of a Candle.” Students will complete this activity in small groups of 3-4. This activity is based on Michael Faraday’s work: “The Chemical History of a Candle” and introduces students to the processes of complete and incomplete combustion using a candle. There are two versions of this activity. Option One (p. 6-10) guides students through the combustion process and the resulting products of incomplete combustion in relation to the Law of the Conservation of Mass. Students are provided with masses of the reactants of the combustion reaction and compare those masses to the masses of the resulting products. They discover that the masses are not equal if they only consider the predicted products of complete combustion. Option Two (p. 16-19) compares complete and incomplete combustion through a series of chemical equations that students have to balance. Successful completion of Option Two requires a solid foundation in general chemistry including the 2 ability to balance intricate chemical equations. The “Life of a Candle” experiments can be found on page 5 of this lesson. Note: The teacher may want to check in with students at various points in Lab 1: “The Life of a Candle” to make sure students are on track (e.g., Questions 3, 5, 9, and 10). Limewater can be prepared by adding five scoops of calcium hydroxide, Ca(OH)2, to approximately two liters of distilled water; a two liter soda bottle makes a good mixing vessel. Shake vigorously then allow the contents to settle overnight. Filter the mixture into a clean bottle. You may have to filter several times to get the desired clarity of the limewater. EXPLAIN Refer back to the anticipatory set and return students’ answers to the questions you asked at the beginning of the lesson. Lead a class discussion comparing a kerosene lamp/Bunsen burner and a candle (e.g., the wick (or solid/melted wax) is not the fuel of the candle or the kerosene lamp. Rather the wax vapor or gas produced is the fuel, just as the liquid kerosene is turned to a gas and supplies the fuel for the lamp or the gas provides fuel for the Bunsen burner.) ELABORATE Once students complete “The Life of a Candle” lab, distribute Comprehension 1: “What is Complete and Incomplete Combustion?” (p. 24-26) for students to complete individually during class or as a homework assignment. At the beginning of the next class (or as class time allows), lead a class discussion to review the Life of a Candle lab and Comprehension 1, and check for understanding. Some possible discussion questions include: • Discuss ways in which firefighters can take advantage of the fire triangle to fight fires. How can the same principles be used at home to improve safety? • Discuss every day activities that might involve incomplete combustion and explain why it is important to understand the dangers? EVALUATE The vocabulary sheets, lab worksheets, Comprehension Guiding Questions, and Evaluation Questions (p. 28 and 29) all offer opportunities for formal assessment. There are numerous opportunities for informal assessment including during the discussions generated from the ‘Engage’, ‘Explain’ and ‘Elaborate’ activities. Equally, teachers should circulate around the lab tables as students work through the lab in order to monitor and evaluate student comprehension. Notes: 3 CO Lesson 1 What is Complete & Incomplete Combustion? – Vocabulary Combustion: Capillary Attraction (Capillary Action): Exothermic: Tetrahedron: Oxidation: Hydrocarbon: Thermal Equilibrium: Hemoglobin: 4 CO Lesson 1 What is Complete & Incomplete Combustion? – Vocabulary Combustion: The process of rapid oxidation that results in burning and a corresponding chemical change, producing heat and light. Capillary Attraction (Capillary Action): The movement of a liquid along the surface of a solid caused by the attraction of molecules of the liquid to the molecules of the solid. Exothermic: A process or reaction that involves the release of heat. Tetrahedron: The shape that is formed from four triangular faces of a polyhedron, which meet at each corner or vertex. Oxidation: When the electrons from a molecule, atom or ion are lost in a chemical reaction. Hydrocarbon: A compound composed of hydrogen and carbon (and often oxygen), including many fuels such as petroleum and natural gas. Thermal Equilibrium: The condition under which two substances in physical contact with each other exchange no heat energy. Hemoglobin: An iron containing protein in red blood cells that transports oxygen. 5 CO Lesson 1 Lab 1:The Life of a Candle – OPTION 1 Guiding Question: How does a candle combust and what products are produced in the process? In this lab, you will use a candle to demonstrate the properties of complete and incomplete combustion. Follow the directions below to complete the experiment. Student Directions: 1. Light the candle and allow it burn until there is consistent flame. Draw a diagram in the space provided below of the candle and flame. Label your diagram with as many details as possible. Bright Yellow Flame Darker Area of Flame Wick Melted Wax Solid Wax 2. Place a white background behind the candle (e.g., a white piece of cardstock or paper but be careful not to ignite the paper). Turn the lights off and shine a flashlight towards the candle. Observe the shadow cast on the white background. Note: You may have to move the flashlight back and forth to get a clearly focused shadow of the candle flame. Summarize your observations. Students should conclude that gas is visible in the shadow casted by the candle flame. This activity also allows students to see that solids or particulates make up part of the flame. 3. Blow out the candle and let the smoke dissipate. Consider some of the other experiences you have had with fire. What does a fire/candle need to burn? With the supplies provided by your teacher, conduct experiments that provide evidence that supports your answer. Explain your findings below. Note to Teacher: Provide students a tea light candle, matches, a glass jar, a wick/piece of twine, and water.