Student Exploration: Energy Conversion

Student Exploration Energy Conversion in a System Vocabulary energy, gravitational potential energy, heat energy, kinetic energy, law of conservation of energy, specific heat capacity Prior Knowledge Questions (Do these BEFORE using the Gizmo.) A battery contains stored energy in the form of chemical energy. What are some examples of devices that are powered by batteries ___________________ _________________________________________________________________________ What different forms of energy are demonstrated by these devices ___________________ _________________________________________________________________________ Gizmo Warm-up Energy constantly changes from one form to another, but in a closed system, the total amount of energy always remains the same. This concept is known formally as the law of conservation of energy. The Energy Conversion in a System Gizmo allows you to observe the law of conservation of energy in action. In the Gizmo, a suspended cylinder has gravitational potential energy. When the cylinder is released, the gravitational potential energy is converted into kinetic energy, which causes the stirrer in the water to spin. What is the initial temperature (T) of the water ___________________________________ Click Play (). What happens as the cylinder drops _____________________________ _________________________________________________________________________ What is the final temperature of the water _______________________________________ Why do you think the temperature of the water increased __________________________ _________________________________________________________________________  Activity A Potential energy and heightGet the Gizmo ready Click Reset (). Introduction The raised cylinder in the Gizmo has gravitational potential energy (GPE) because gravity can cause the cylinder to drop. When the cylinder drops, its kinetic energy is converted into heat energy, which raises the temperature of the water.Question How does the cylinders initial height affect its gravitational potential energy Predict How do you think increasing the cylinders height will affect the final temperature of the water Gather data Make sure the waters Mass is 1.0 kg, its Temp is 25 C, and the cylinders Mass is 5 kg. Set the cylinders Height to 100 m. (Note The large height scale used by the Gizmo, while not practical in a real-world experiment, makes it easier to produce observable temperature changes in the water.) Click Play, and record the waters final temperature in the table below. Repeat the experiment at each cylinder height to complete the second column in the table. Cylinder height (m)Final temp. (C)Change in temp. (C)Cylinder GPE (J)100 m26.17c-0.174,900200 m27.34c-2.349,800500 m30.86c-5.8624,5001,000 m36.72c-11.7249,000 Calculate Subtract the waters initial temperature from its final temperature to complete the third column of the table. An objects GPE can be calculated by multiplying its height (h) by its mass (m) and acceleration due to gravity (g) GPE mgh. On Earth, g 9.8 m/s2. Calculate the cylinders GPE for each of the trials you completed and fill in the last column of the table. Analyze Study the data you collected. How does doubling the height of the cylinder affect its GPE ___________________ ___________________________________________________________________ How does doubling the cylinders GPE affect the change in temperature experienced by the water ________________________________________________________ Activity B Potential energy and massGet the Gizmo ready Click Reset (). Predict How do you think increasing the cylinders mass will affect the final temperature of the water Explain your prediction. _____________________________________________ _________________________________________________________________________ Gather data Make sure the waters Mass is still set to 1.0 kg and its Temp is 25 C. Set the cylinders Height to 500 m. Use the Gizmo to complete the second column of the table below, and then calculate the change in temperature and the cylinders GPE for each trial. Cylinder mass (kg)Final temp. (C)Change in temp. (C)Cylinder GPE (J)1 kg25 -0.12 500 2 kg25.12 -0.23 490 5 kg25.23 -0.35 480 10 kg25.35-0.35470 Compare Describe any patterns you see and compare your results with the results you got when experimenting with the cylinders height in activity A ___ It has decrease in the final temp._______________________ _________________________________________________________________________ _________________________________________________________________________ Apply Suppose the cylinder had a mass of 20 kg and started at a height of 2,000 m. If the initial temperature of the water was 25 C, what would be the final temperature Explain. ____________ The final temp would probably be 50, because the higher the cylinder is the higer the temp goes._____________________________________________________________ _________________________________________________________________________ Activity C Heat energy and temperatureGet the Gizmo ready Click Reset. Select the GRAPH tab and choose the Generated heat option. Question What factors affect how much the waters temperature changes when a given amount of heat energy is added to the water Form hypotheses In activity A, you discovered how changing the cylinders GPE affects the waters final temperature. Now consider the following questions How will changing the waters initial temperature affect how much the waters temperature increases when the cylinder is dropped ___________________________________________________________________ How will changing the waters mass affect how much the waters temperature increases when the cylinder is dropped ___________________________________________________________________ Gather data Set the cylinders Mass to 5 kg and its Height to 500 m. Use the Gizmo to test each of the scenarios listed in the table and record your results in the last three columns. Use the graph to estimate the generated heat. Waters mass (kg)Waters initial temp. (C)Waters final temp. (C)Change in temp. (C)Generated heat (kJ)1 kg0 C1 kg20 C1 kg40 C0.5 kg25 C1 kg25 C1.5 kg25 C Explain Why was the amount of heat generated the same each time _________________ _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ Activity C (continued from previous page) Analyze Use the data you collected to answer the following questions. What was the effect of the initial temperature on the temperature change of the water, and why do you think this happened ___________________________________________________________________ __________________________________________________________________ What was the effect of doubling the water mass on the temperature change, and why do you think this happened ___________________________________________________________________ ___________________________________________________________________ What is the gravitational potential energy of the cylinder _______________ If no energy is lost, how much heat energy is added to the water _______________ What is the mass of the water _______________ What is the temperature change of the water _______________ What is the specific heat of the water (Show your work below.) _______________ How does the specific heat of water compare to the specific heat of iron _________ ___________________________________________________________________ 10-20-14 camera, flash light Radio, and toys. Kinetic Energy 25c The temperature rises to 29.69c 29.69c Because while the cylinder was was dropping the fan was spinning thus making the water temperature change. spin, so the temperature will rise higher. Because the higher the cylinder is the longer it falls and the longer the it will It gives the can more It affects the water final temperature. because of the heat that is getting the water. 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