Energy end-of-unit assessment

Transcription

1 Objective items 1. What is the source of energy in the following situations? (3marks) a. a girl pedals her bicycle along the street Food eaten by the girl. (1) b. a drag racing car spins its tyres and hurtles down the track Petrol. (1) c. a eucalyptus tree grows to a height of 80 m. Sunlight. (1) 2. Each of the machines listed below wastes some energy when it operates. Complete the table by listing the desired forms of energy and the waste forms of energy produced by each machine. (6 marks) Machine Desired forms of energy Types of waste energy Electric light globe Light (1) Heat (1) Electric food mixer Movement (1) Sound (0.5) and heat (0.5) Car engine Movement (1) Sound (0.5) and heat (0.5) 3. Indicate which of the following energy sources are renewable () O non-renewable (N). (3 marks) 0.5 marks for each correct answer. Energy source or N Coal N Solar Wind Wood Uranium N Natural gas N 4. What are the main advantages and disadvantages of the following sources of energy? (6 marks) One mark for each acceptable answer per table. Source of energy Advantage Disadvantage Gas Nuclear Wind Easy to distribute to point of use or clean burning producing few oxides of nitrogen or sulphur. A small amount of fuel produces huge quantities of useable energy or does not generate greenhouse gases. Low recurrent costs of generation or renewable or non-polluting. Generates carbon dioxide a greenhouse gas. adioactive wastes are radioactive and difficult to store. Wind speed is highly variable. Commonwealth of Australia,

2 5. A model rocket with a fuel motor is launched from the ground. It flies to a height of 100 m and then falls back to the ground. (8 marks) a. Complete the table to show the types of energy present at each stage of the flight. Stage of flight Types of energy present 1. The rocket is sitting on the launch pad. Chemical potential energy (0.5) 2. The rocket has been fired and is now 20 m off the ground. 3. The fuel is used up, the motor has cut out and the rocket has reached its maximum height, it is still and about to fall back towards the ground. 4. The rocket is falling back towards the ground. Chemical potential energy (0.5) Kinetic energy (0.5) Sound energy (0.5) Gravitational potential energy (0.5) Gravitational potential energy (0.5) Potential energy (0.5) Kinetic energy (0.5) 5. The rocket is back on the ground. b. At which stage did the rocket have the greatest total energy? On the launch pad (1) c. At which stage did the rocket have least total energy? On ground after the flight (1) 6. Consider the experimental results in the tables below and the way you would plot graphs of the results. a. Electricity generated by a wind turbine. Wind speed (km/h) Electricity generated kw/h What type of graph would you use? Line graph (1) Which variable would you plot on the horizontal axis of the graph? Wind speed (1) b. Electricity generated by a bank of solar cells under different cloud conditions. (2 marks) Electricity generated kw/h Cloud cover 5 Complete cloud cover 23 Many clouds 65 Few clouds 122 Clear sky What type of graph would you use? Bar graph (1) Commonwealth of Australia,

3 Which variable would you plot on the horizontal axis of the graph? Cloud cover (1) 7. One advantage of solar energy is that it: a. is not renewable b. is efficient in any climate c. is available at all times d. is non-polluting. Extended response items For items 9 and 12, use separate sheets of paper. 8. For her definition of energy, Helen wrote Energy is a substance that can move or change the movement of something. Comment on Helen s definition. How would you improve it? (5 marks) Any valid five points for a total of five marks. Energy is not a substance. (1) Forces move or change the movement of things rather than energy. (1) Energy enables things to change eg energise forces that make things move. (1) Energy enables many types of changes, not just changes in movement. (1) Changes in objects are associated with transfers and transformations of energy. (1) Energy is the capacity to do work or energy makes things happen. (1) 9. Write a short newspaper story (about 2/3 of a page) about the day when the world runs out of fossil fuels (about 175 years in the future). In your story explain the history of energy use by humans and how future generations will meet their energy needs. Make sure you include a headline for your story. (10 marks) Any valid points up to a maximum of 10 marks, including up to two marks for communicating clearly. Suitable headline. (1) Wood an important early fuel for fires used for cooking and keeping warm (1) later supplemented by other fossil fuels such as coal. (1) Industrial revolution saw huge increase in use of fossil fuels such as coal and gas. (1) The development of motor cars and petroleum-based fuels led to a huge increase in oil consumption. (1) With concerns about the greenhouse effect (1) and increasing costs of fossil fuels greater use made of nuclear energy (1) and renewable energy sources such as solar, wind and hydro. (1) Great efforts made to increase the efficiency of energy use as costs of energy rise. (1) 10. As fossil-fuel energy sources get used up, which energy sources do you think would make the best substitutes for them? (5 marks) Any valid points up to a maximum of five marks. enewable sources such as solar and wind have the advantage of being nonpolluting (1), and do not add to the greenhouse effect (1), however there are concerns about continuity of supply (1) and initial capital costs. (1) Commonwealth of Australia,

4 Nuclear energy has the potential to provide a large energy supply (1) does not add to the greenhouse effect (1), however there are concerns about waste storage and disposal. (1) 11. It is expected that the cost of electricity will increase considerably over the next 10 years. How could typical Australian families make the greatest savings in electricity consumption in their homes? (5 marks) Any valid points up to a maximum of three marks. Purchase energy efficient appliances. (1) Make greater use of passive solar house designs. (1) Make greater use of insulation. (1) Install solar hot water heaters. (1) 12. Draw an energy chain diagram to show how the potential energy of water in a dam is converted into electricity in a hydroelectric power plant. Include in your diagram any forms of waste energy produced by the power plant. (5 marks) Maximum of five marks for including any of the following valid points. Potential energy of water in dam. (1) Kinetic energy of water flowing down to turbine. (1) Kinetic energy of turbine and generator. (1) Electrical energy produced by turbine. (1) Waste heat (1) and sound energy (1) produced by the turbine and generator. 13. What changes will we have to make to our uses of energy if air pollution and the greenhouse effect are to be reduced? (3 marks) Maximum of three marks for including any of the following valid points. Must reduce use of coal-powered electricity generation. (1) Must reduce use of petroleum-based fuels for transportation. (1) Greater use of public transport. (1) Increase efficiency of energy use. (1) 14. Electrical energy is used to power a lamp. The amount of light energy produced is: a. more than the amount of electrical energy used b. the same as the amount of electrical energy used c. less than the amount of electrical energy used. Give a reason to support your answer: Some of the electrical energy is transformed into heat, which is a waste of energy. (1) Activity-based items 15. Elastic band energy Materials required: 3 different elastic bands, 35 cm ruler and a spring balance Procedure 1. Take one of the elastic bands, hook it over the end of your ruler and use the spring balance to pull the band until it is stretched to the 12 cm mark of your ruler. ecord the reading on the spring balance. 2. epeat for each elastic band and make sufficient measurements so that you can compare the three elastic bands. Commonwealth of Australia,

5 3. ecord all of your measurements. Questions 1. Which band required the greatest force to stretch it to 12 cm? How confident are you of this? Explain. 2. What type of energy does the band have when it is stretched? 3. If you were to plot a graph of your results, what type of graph would you draw? Which variable would you plot on the horizontal axis of the graph? 4. How could you have improved your investigation? A maximum of 10 marks for any of the following valid points. esults recorded in an organised table. (1) Made repeat measurements. (1) Averaged repeat measurements so that a comparison could be made. (1) Conclusion drawn about which band required the greatest force to stretch it consistent with the collected data. (1) ecognises that error is associated with the measurements. (1) Elastic potential energy. (1) Bar graph if bands identified by colour, number or alphabet letter. (1) Line graph if bands identified by initial unstretched length. (1) Elastic band is plotted on horizontal axis. (1) Any valid suggestion for improving the design, methods or techniques. (1) Commonwealth of Australia,