FOSSIL FUEL COMBUSTION:

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1 Science 30 Unit B Chemistry and the Environment Outcome 1: Students will analyze the sources of acids and bases and their effects on the environment. Specific Outcome 1.8: Outline the chemical reactions that produce air pollutants that, when combined with water, ultimately result in acid deposition. Textbook reference pages: p in Science 30 Products of Combustion Reactions Working as a team in a local dogsled race, Kayla and her dogs challenge the cold and their physical limits. They are all working and breathing hard. With each breather Kayla and her dogs take, they must exhale the products of Cellular Respiration - a process that converts the chemical potential energy within food into a form the body s muscles can use. Cellular Respiration the process by which cells convert the chemical energy stored in organic molecules (sugars) into energy that cells can use. - Reactants: Glucose (C6H12O6) + O2(g) - Products: CO2(g) + H2O(g) + ATP (energy) COMBUSTION REACTIONS - COMBUSTION: o Requires: Fuel and Oxygen o Releases: Energy - FOSSIL FUEL COMBUSTION: o Reactants: hydrocarbon (ethane, propane, methane, etc.) HYDROCARBONS are organic compounds that contain HYDROGEN and CARBON atoms o Products: CO2(g) + H2O(g) (possibly others, depending on impurities found in the reactant) 1

2 - CH4(g) + 2 O2(g) CO2(g) + 2 H20(g) o Complete combustion occurs when there is sufficient enough oxygen O2(g) - 2 CH4(g) + 3 O2(g) 2 CO(g) + 4 H20(g) o Incomplete combustion occurs when there is a lack of O2(g) o Produces CO (Carbon Monoxide) along with CO2 (Carbon Dioxide) - COMBUSTION, like any chemical reaction, involves collisions between the molecules of the reactants. o This results in the formation of CARBON DIOXIDE AND WATER (products). Example: CH4(g) + O2(g) CO2(g) + H2O(g) Methane (hydrocarbon) Carbon Dioxide Emissions and Combustion Because we have a hydrocarbon (methane) and it produces carbon dioxide (NOT carbon monoxide), we know this is COMPLETE COMBUSTION - During most combustion reactions, the oxides produced are released into the atmosphere. o These are called EMISSIONS Emissions include a) oxides of CARBON b) oxides of NITROGEN c) oxides of SULFUR 2

3 OXIDES OF CARBON 1. Carbon Dioxide: Carbon dioxide can enter our atmosphere through COMBUSTION and NATURAL SOURCES. COMBUSTION: - Burning carbon compounds (like wood and other forms of BIOMASS plant matter/agricultural waste or hydrocarbon molecules) creates CARBON DIOXIDE NATURAL SOURCES: - Cellular Respiration, forest fires, volcanic eruptions and weather of some rocks releases carbon dioxide into the atmosphere naturally. (CARBON CYCLE) Problem with a buildup of carbon dioxide in the atmosphere - CO2 is a greenhouse gas (it holds in thermal energy. An increase in CO2 increases thermal energy retention, which increases overall atmospheric temperatures) 3

4 2. Carbon Monoxide - Carbon Monoxide is produced during combustion with limited O2(g) (incomplete combustion) - Where does carbon monoxide come from? o AUTOMOBILE EMISSIONS (eg. Car engines) - Problems with carbon monoxide? o bonds to hemoglobin, preventing O2 from bonding, preventing O2(g) from reaching body tissues, resulting in cell death QUESTION: A. Refer to the diagram of the carbon cycle on page 157. Explain how the increased use of combustion processes by society and deforestation could result in a higher level of atmospheric carbon dioxide, a level that cannot be removed by natural mechanisms. An increase in combustion processes could result in an increase in the amount of carbon dioxide in the atmosphere if the speed at which carbon dioxide is produced is greater than the speed at which carbon dioxide can be removed from the atmosphere. BALANCING CHEMICAL FORMULAS - All chemical reactions must begin and end with the same atoms, in the same proportions - Recall from earlier science courses, this requires you to balance all chemical equations Examples: 1. 2 C2H6(g) + 7 O2(g) 4 CO2(g) + 6 H2O(g) 2. 1 CH4(g) + 2 O2(g) 1 CO2(g) + 2H2O(g) 3. 1 C5H12(g) + 8 O2(g) 5 CO2(g) + 6 H2O(g) 4. 1 C4H8(g) + 6 O2(g) 4 CO2(g) + 4 H2O(g) 5. 2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g) 6. Combustion of Octane, C8H18(g) 2 C8H18(g) + 25 O2(g) 16 CO2(g) + 18 H2O(g) 4

5 OXIDES OF SULFUR Natural resources: - Sulfur is an element that is found in small quantities within many HYDROCARBONS. o Examples: Coal (in Alberta) has low sulfur but in Eastern Canada, Coal has a higher sulfur content Crude oil and oil sands also have sulfur Natural Gas has sulfur in the form of H2S (sour gas toxic to humans!) SOUR GAS natural gas that contains greater than 1% hydrogen sulfide o SOUR GAS when processed and sent to your home, removes the hydrogen sulfide through a process called SWEETENING. (YOU GET RID OF THE SOUR AND MAKE IT SWEET ) o 40% of the natural gas reserves in Alberta are SOUR! We have a lot of sweetening to do! Sulfur dioxide (SO2) and Sulfur trioxide (SO3) - Low quality natural gas is FLARED this process converts that H2S (Sour Gas) to SO2 and SO3 o How the flaring process works: Sour gas is mixed with water to produce either sulfur dioxide or sulfur trioxide. - Sulphur dioxide (SO2) and sulphur trioxide (SO3) gases are emitted into the atmosphere during the process that removes H2S(g) from natural gas. - Another major source of SOX is the combustion of fossil fuels containing sulphur 5

6 Sulphur removed from sour gas in SW Alberta OXIDES OF NITROGEN Earth s atmosphere is 78% NITROGEN (N2(g) a normally unreactive gas) High temperatures of combustion cause nitrogen to react, producing NO(g) (Nitrogen monoxide) and NO2(g) (nitrogen dioxide) o Oxides of nitrogen are commonly referred to as NOx COMPOUNDS o NOx emission levels tend to change depending on: COMBUSTION OF FOSSIL FUELS (they are higher near urban areas) SEASONS (temperature) 6

7 Sulphur oxides (SOX) and nitrogen oxides (NOX) in the atmosphere cause acid rain Issues with Combustion: 1. METAL PARTICLES can be present in combustion emissions a. Example: Coal contains trace amounts of both MERCURY AND LEAD i. THESE POISON YOU! 2. PARTICULATE MATTER (small solids suspended in the atmosphere) a. Soot, smoke, ash (from industry and forest fires), soil particles, pollen 7

8 i. These things contribute to asthma and other lung diseases. Name: Particulate Matter (PM) Hydrocarbon combustion contributes to particulate matter tiny particles suspended in the atmosphere PM can be smaller than the width of a human hair 8

9 Practice questions: Page 159 # 4 & 5 4. complete combustion: CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) incomplete combustion: 2 CH4(g) + 3 O2(g) 2 CO(g) + 4 H2O(g) 5. The complete combustion of methane uses more oxygen per molecule of methane, 2O2: 1CH4, than the incomplete combustion of methane, 3O2: 2CH4 or 1.5O2: 1CH4. Page 160, #7 & 8 7. Emissions of NOx are the result of vehicle emissions and combustion processes that use atmospheric air (e.g., furnaces). The higher concentration of people in urban areas homes, vehicles, and so on results in higher emissions. Also, large industries tend to be located near urban areas, which adds to NOx emissions. 8. a. NOx emissions will increase. There are more vehicles on the road during rush hour. b. NOx emissions will increase. A cold snap in winter increases furnace use to heat homes. It also increases idling time of vehicles as they warm up. c. NOx emissions will increase. A heat wave in summer increases the demand on power plants due to the electricity needed to operate air conditioners. Page 164, # a. Combustion is a chemical process involving a reaction of a substance with oxygen. Combustion is a major source of emissions. b. An oxide is a chemical substance consisting of oxygen and another element. Many chemical compounds are present as oxides (e.g., carbon dioxide, nitrogen oxides, and sulfur oxides) in emissions. c. Pollution consists of waste substances that contaminate or harm their surroundings. This lesson describes some of the sources and common forms of pollution. d. A greenhouse gas is a substance that is capable of absorbing infrared radiation (heat) and preventing its loss. Greenhouse gases act to trap energy in the atmosphere, contributing to global climate change. Carbon dioxide, a product of the combustion of hydrocarbons, is a greenhouse gas. e. Hemoglobin is a molecule in blood that is responsible for the transport of oxygen. Emissions like carbon monoxide can bind to hemoglobin, affecting oxygen transport in the human body and, thus, affecting health. f. Sour gas is a natural gas containing hydrogen sulfide, H2S(g). A great deal of sour gas is extracted in Alberta, and there may be concerns about the effects of this process on the environment. 9

10 g. NOx represents the oxides of nitrogen nitrogen monoxide, NO(g), and nitrogen dioxide, NO2(g) and is a by-product of combustion processes. Nitrogen is usually not present in the fuel, but it can be a product of the process. h. Particulate matter consists of tiny particles from emissions that are suspended in air. Particulate matter may consist of larger particles and may be visible. It is significant because it is a health hazard. i. A carcinogen is a substance that may cause cancer. Carcinogens are a major threat to health and should be avoided. 2. Bonds between the atoms of the fuel are broken and new combinations between the atoms of the fuel and (most often) oxygen form, releasing energy. 3. If carbon is in the substance being combusted, carbon monoxide and carbon dioxide may be produced. Likewise, if sulfur is in the substance being combusted, sulfur dioxide may be produced. 4. Nitrogen oxides can appear in a variety of forms, like NO(g) and NO2(g). The subscript x refers to the number of oxygen atoms that may be present. 5. a. 1 CH4(g) + 2 O2(g) 1 CO2(g) + 2 H2O(g) b. 2 C2H6(g) + 7 O2(g) 4 CO2(g) + 6 H2O(g) c. 1 C3H8(g) + 5 O2(g) 3 CO2(g) + 4 H2O(g) 6. The air drawn into internal combustion engines consists mostly of nitrogen. Some of the energy released by the combustion process enables the combination of nitrogen and oxygen to form NOx compounds. 7. a. thermal step: 2 H2S(g) + O2(g) 2 S(s) + 2 H2O(g) 2 H2S(g) + 3 O2(g) 2 SO2(g) + 2 H2O(g) catalytic step: 2 H2S(g) + SO2(g) 3 S(s) + 2 H2O(g) b. NOx compounds are produced in the thermal step. The high-temperature combustion process uses atmospheric air in the combustion chamber (like most furnaces). c. Using pure oxygen will remove nitrogen from the combustion chamber. If nitrogen is not present in the combustion chamber, the emission of NOx compounds is avoided. 10

11 INVESTIGATION: Comparing the Effects of the Products of Cellular Respiration Background Info: Cells use molecules within food as an energy source. Cellular respiration is a process similar to the combustion of hydrocarbons in that oxygen is required, carbon dioxide and water are produced, and energy is released. Purpose: Look at the effects of the products of cellular respiration. Materials: mL Erlenmeyer Flask - 75-mL of distilled water - Bromothymol Blue Indicator mL graduated cylinder - Drinking straw - Eye dropper - Stop watch Procedure: 1. Use the graduated cylinder to measure 75-mL of distilled water; then transfer the water to the Erlenmeyer Flask. 2. Add four drops of bromothymol blue to the distilled water. Note the color of the mixture. 3. Insert the drinking straw into the mixture in the flask, and exhale through the straw until the color of the indicator changes to yellow. Record the time taken for the indicator to change color. Observations: Color of Indicator before exhaling Time taken for indicator to turn yellow Analysis: 1. Explain the significance of the color change 11

12 2. Identify the reason for the mixture to change color. HINT: see ``acid and base indicators`` table on page Write the balanced chemical equation for the cellular respiration of glucose C6H12O6(aq). 4. Hypothesize the effect that carbon dioxide released by many processes could have on water within the biosphere. 12

13 ACTIVITY: Taking a stand Emissions Testing Name: Albertans have a high dependence on the cars and trucks they drive for pleasure or for work. In addition, Albertans enjoy their recreations vehicles (ie: motorcycles, quads, boats and snowmobiles). Albertans also place a high priority on their health and the health of the diverse habitants that exist throughout the province. As you know, pollution from vehicles affects both society and the environment. Is it time to place standards on the emissions from vehicles? Currently, three Canadian provinces British Columbia, Ontario and New Brunswick have emission-testing programs for vehicles. Should Alberta be next? Purpose: You will debate the following question: Should Alberta have an emission-testing program for vehicles similar to those used in BC, ON and NB? Background Information: Before you begin, use the Internet to answer the following questions: 1. Why is emission testing required in some provinces and not in others? In provinces that have emissions-testing programs, are all vehicles tested in all regions of the province? 2. Identify the reason for initiating emissions-testing programs in these provinces. 3. List the items being tested for during an emissions test. 4. What do emissions tests cost consumers in the province with testing programs? 13

14 Procedure: 1. Prepare a position statement that clearly defines whether you support or do not support mandatory emissions testing of all vehicles in Alberta. When developing your position statement, review the list of perspectives listed on page 590 in the text. Use this list to help justify your position. 2. Prepare a rebuttal a second statement that responds to a criticism of your position. When preparing your rebuttal, imagine you are the opponent in the debate. What part of your position statement would your opponent most likely challenge? Would it be the credibility of the information you present or the conclusions you make? Your rebuttal is your opportunity to develop a plan to further defend your position. 14