STATE DA VINCI DECATHLON 2017

Transcription

1 STATE DA VINCI DECATHLON 2017 CELEBRATING THE ACADEMIC GIFTS OF STUDENTS IN YEARS 7 & 8 SCIENCE TEAM NUMBER 1

2 The Coal Paradox: We can't live without it. But can we survive with it? On a scorching August day in southwestern Indiana, the giant Gibson generating station is running flat out. Its five 180-foot-high (54.9-meter-high) boilers are [burning] 25 tons (22.7 metric tons) of coal each minute, sending thousand-degree (578-degree- Celsius) steam blasting through turbines that churn out more than 3,000 megawatts of electric power, 50 percent more than Hoover Dam. The plant s cooling system is struggling to keep up, and in the control room warnings chirp as the exhaust temperature rises. But there's no backing off on a day like this, with air conditioners humming across the Midwest and electricity demand close to record levels. Gibson, one of the biggest power plants in the country, is a mainstay of the region's electricity supply, pumping enough power into the grid for three million people. Next time you turn up the AC or pop in a DVD, spare a thought for places like Gibson and for the grimy fuel it devours at the rate of three 100-car trainloads a day. Coal-burning power plants like this one supply the United States with half its electricity. They also emit a stew of damaging substances, including sulfur dioxide a major cause of acid rain and mercury. And they gush as much climate-warming carbon dioxide as America's cars, trucks, buses, and planes combined. For the past 15 years U.S. utilities needing to add power have mainly built plants that burn natural gas, a relatively clean fuel. But a near tripling of natural gas prices in the past seven years has idled many gas-fired plants and put a damper on new construction. Neither nuclear energy nor alternative sources such as wind and solar seem likely to meet the demand for electricity. Extract from Appenzeller, T., National Geographic, The Coal Paradox, 2006 INSTRUCTIONS Read the information above Attempt all the following questions 2

3 QUESTIONS 1. Using information from the opening stimulus and the given labels, draw a pictorial representation of a coal power plant: (4 marks) Labels Generator Turbines Water Source Steam Power Lines Coal Furnace Exhaust Tower Cooling water (condenser) 3

4 2. Identify possible sources of environmental damage or pollution that could be caused by a coal power plant like the one pictured above. (3 marks) 3. Below is a partial flowchart to represent the production of electrical energy from coal in the ground. Identify at least 5 ways that could reduce the amount of energy that is generated by this system. Consider processes before, during and after this particular flowchart. (5 marks) High quality, pure anthracite coal Combustion Thermal energy Boiling Steam pressure transferred to water turns a turbine Electricity reaches home Conduction in long wires The motor effect Electricity generated by turbine movement 4

5 I. II. III.. IV. V.. 4. In the final step of the above flowchart, an electrician needs to test certain metals to identify, which will conduct the electricity with the highest efficiency. Identify the variables in this experiment. (3 marks) Independent Dependent Controlled (give two) I. II. 5

6 5. There are three levels of classification for coal: lignite, bituminous and anthracite. A summary of the characteristics of each type of coal is given in the table below: Type Approximate Energy Content Pollutant Relative Depth Age (years) (MJ/kg) Content Bituminous 100 million 20 Moderate Moderate Anthracite 200 million 40 Low Lowest Lignite 40 thousand 2 High Highest a. Draw a neat graph to represent the relationship between the approximate age of coal and the energy content of that type (3 marks) b. Describe the relationship seen in your graph (1 mark) c. Describe the relationship between the relative depth and age of the types of coal (1 mark) 6

7 d. Suggest a reason why anthracite would have the highest energy content. (2 marks) 6. Like the carbon compounds in coal, sulfur can also combust to form sulfur dioxide (react with oxygen). However, this reaction releases much less energy than the equivalent reactions in coal. Hence, also considering other stimulus in this booklet, explain why coal with a low sulfur content is preferred. (3 marks) 7

8 7. Using the following description, write out a sequence of three chemical equations to demonstrate the formation of acid rain from sulfur dioxide: (3 marks) First sulfur dioxide is oxidized in oxygen gas, O 2(g), to produce sulfur trioxide. This is then reacted with concentrated sulfuric acid, H 2 SO 4(l), to prevent an uncontrollable reaction in water. In this reaction, fuming sulfuric acid or oleum, H 2 S 2 O 7(l), is formed. Oleum can be safely reacted with water to produce double the sulfuric acid that was originally used to produce the oleum. 8. For each of the following sources of renewable energy that could replace fossil fuels, provide a short explanation of how the process extracts energy from the natural situation. (2 marks each) a. Solar Panels: 8

9 b. Hydroelectricity:. c. Geothermal Heat Pumps:. d. Wind Turbines/Farms:. 9

10 9. For each of the energy sources in question 1, identify the forms of energy and types of energy transformations that occur from the natural material to the final usable electricity. (2 marks each) a. Solar Panels:. b. Hydroelectricity:. c. Geothermal Heat Pumps:. 10

11 d. Wind Turbines/Farms:. 11

12 STATE DA VINCI DECATHLON 2017 CELEBRATING THE ACADEMIC GIFTS OF STUDENTS IN YEARS 7 & 8 SCIENCE ANSWERS TEAM NUMBER 1

13 The Coal Paradox: We can't live without it. But can we survive with it? On a scorching August day in southwestern Indiana, the giant Gibson generating station is running flat out. Its five 180-foot-high (54.9-meter-high) boilers are [burning] 25 tons (22.7 metric tons) of coal each minute, sending thousand-degree (578-degree- Celsius) steam blasting through turbines that churn out more than 3,000 megawatts of electric power, 50 percent more than Hoover Dam. The plant s cooling system is struggling to keep up, and in the control room warnings chirp as the exhaust temperature rises. But there's no backing off on a day like this, with air conditioners humming across the Midwest and electricity demand close to record levels. Gibson, one of the biggest power plants in the country, is a mainstay of the region's electricity supply, pumping enough power into the grid for three million people. Next time you turn up the AC or pop in a DVD, spare a thought for places like Gibson and for the grimy fuel it devours at the rate of three 100-car trainloads a day. Coal-burning power plants like this one supply the United States with half its electricity. They also emit a stew of damaging substances, including sulfur dioxide a major cause of acid rain and mercury. And they gush as much climate-warming carbon dioxide as America's cars, trucks, buses, and planes combined. For the past 15 years U.S. utilities needing to add power have mainly built plants that burn natural gas, a relatively clean fuel. But a near tripling of natural gas prices in the past seven years has idled many gas-fired plants and put a damper on new construction. Neither nuclear energy nor alternative sources such as wind and solar seem likely to meet the demand for electricity. Extract from Appenzeller, T., National Geographic, The Coal Paradox, 2006 INSTRUCTIONS Read the information above Attempt all the following questions 2

14 QUESTIONS 1. Using information from the opening stimulus and the given labels, draw a pictorial representation of a coal power plant: (4 marks) Labels Generator Turbines Water Source Steam Power Lines Coal Furnace Exhaust Tower Cooling water (condenser) Example Diagram: 2. Identify possible sources of environmental damage or pollution that could be caused by a coal power plant like the one pictured above. (3 marks) Answers may include, but are not limited to: - Thermal pollution caused by discharging hot water back in to the river - Landslide/collapse due to empty spaces left where the coal was mined - CO2 gas given off by combustion of the coal - Sulfur dioxide/nitrogen oxides given off by combusting impurities in the coal - Smoke given off from tower causing smog/haze 1 mark per valid point 3

15 3. Below is a partial flowchart to represent the production of electrical energy from coal in the ground. Identify at least 5 ways that could reduce the amount of energy that is generated by this system. Consider processes before, during and after this particular flowchart. (5 marks) High quality, pure anthracite coal Combustion Thermal energy Boiling Steam pressure transferred to water turns a turbine Electricity reaches home Conduction in long wires The motor effect Electricity generated by turbine movement Answers may include, but are not limited to: - Mining of coal - Physical processes (crushing/grinding) to purify coal - Vehicle energy to transport coal - Incomplete combustion - Escape of thermal energy into pipes/atmosphere instead of water - Escape of hot steam via pipe leaks - Power loss in electrical transmission due to heat/light/noise - Faulty connections for wiring 1 mark per valid point 4. In the final step of the above flowchart, an electrician needs to test certain metals to identify, which will conduct the electricity with the highest efficiency. Identify the variables in this experiment. (3 marks) Independent: Metal used for wires Dependent: Amount of energy transferred to the end of the wire Controlled: Any two of: temperature, thickness of wire, initial electrical energy put into wire, 4

16 Energy Content (MJ/kg) 5. There are three levels of classification for coal: lignite, bituminous and anthracite. A summary of the characteristics of each type of coal is given in the table below: Type Approximate Energy Content Pollutant Relative Depth Age (years) (MJ/kg) Content Bituminous 100 million 20 Moderate Moderate Anthracite 200 million 40 Low Lowest Lignite 40 thousand 2 High Highest a. Draw a neat graph to represent the relationship between the approximate age of coal and the energy content of that type (3 marks) Effect of Coal Age on Energy Content Approximate Age (years) b. Describe the relationship seen in your graph (1 mark) Linear, directly proportional c. Describe the relationship between the relative depth and age of the types of coal (1 mark) Inversely proportional d. Suggest a reason why anthracite would have the highest energy content. (2 marks) 5

17 - Anthracite contains less pollutants so for the same mass, it will produce more energy from the pure coal - Anthracite is found at a lower depth so it has been under higher pressure. Hence, it will be more dense and contain more energy producing coal for the same volume 6. Like the carbon compounds in coal, sulfur can also combust to form sulfur dioxide (react with oxygen). However, this reaction releases much less energy than the equivalent reactions in coal. Hence, also considering other stimulus in this booklet, explain why coal with a low sulfur content is preferred. (3 marks) - High-sulfur content coal will release less energy on combustion - Sulfur dioxide also contributes to acid rain which has many environmental and social impacts as a pollutant (see initial stimulus) - Hence, power plants prefer low-sulfur coal to increase their energy output and preserve the environment around the plant 7. Using the following description, write out a sequence of three chemical equations to demonstrate the formation of acid rain from sulfur dioxide: (3 marks) First sulfur dioxide is oxidized in oxygen gas, O 2(g), to produce sulfur trioxide. This is then reacted with concentrated sulfuric acid, H 2 SO 4(l), to prevent an uncontrollable reaction in water. In this reaction, fuming sulfuric acid or oleum, H 2 S 2 O 7(l), is formed. Oleum can be safely reacted with water to produce double the sulfuric acid that was originally used to produce the oleum. - Ignore equilibrium arrows SO 2(g) + O 2(g) SO 3(g) SO 3(g) + H 2 SO 4(l) H 2 S 2 O 7(l) H 2 S 2 O 7(l) + H 2 O (l) 2H 2 SO 4(l) 6

18 8. For each of the following sources of renewable energy that could replace fossil fuels, provide a short explanation of how the process extracts energy from the natural situation. (2 marks each) a. Solar Panels: - Both thermal and electromagnetic (light) energy from the Sun reaches Earth and is converted into usable electricity by solar panels on exposed areas such as house roofs. This energy is constantly hitting the Earth - Extra detail: The Sun is effectively a nuclear reactor, where nuclear fusion releases huge amounts of energy as heat and light, which travels through space to the Earth b. Hydroelectricity: - Water moves in various situations: o Falling from a high point in a waterfall o Tidal flows due to the Moon s gravitational pull o River currents as they slope downhill due to gravity - This movement can be used to turn turbines. Hence, in a similar situation to coal, this movement can be converted to useable electricity c. Geothermal Heat Pumps: - The centre of the Earth is much warmer than the surface, and all of this heat can be accessed by digging down into the ground - Heat can be pumped upwards either directly into houses/buildings, or used to turn turbines as well to produce electricity 7

19 d. Wind Turbines/Farms: - Moving air particles that constitute a wind flow over the arms of a wind turbine and cause it to begin spinning - This spinning motion can be used to generate electricity just like in the coal power plant 9. For each of the energy sources in question 1, identify the forms of energy and types of energy transformations that occur from the natural material to the final usable electricity. (2 marks each) a. Solar Panels: - Thermal/Light energy - Electrical energy b. Hydroelectricity: - Gravitational potential energy - Kinetic energy - Electrial energy c. Geothermal Heat Pumps: - Thermal energy directly - OR Thermal energy to electrical energy d. Wind Turbines/Farms: - Kinetic Energy - Electrical Energy 8