Student Exploration- Energy Conversion in a System (ANSWER KEY)

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.
1. What are some examples of devices that are powered by batteries?
2.What different forms of energy are dmonstrated 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.
1. What is the initial temperature (T) of the water?
2.Click Play ( ). What happens as the cylinder drops
3.What is the final temperature of the water
4.Why do you think the temperature of the water increased
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 cylinder’s initial height affect its gravitational potential energy?
1. Predict: How do you think increasing the cylinder’s height will affect the final temperature of the water?
2. Gather data: Make sure the water’s Mass is 1.0 kg, its Temp is 25 °C, and the cylinder’s Mass is 5 kg. Set the cylinder’s 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 water’s final temperature in the table below. Repeat the experiment at each cylinder height to complete the second column in the table
3.Calculate: Subtract the water’s initial temperature from its final temperature to complete the third column of the table.
An object’s 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 cylinder’s GPE for each of the trials you completed and fill in the last column of the table
4. Analyze: Study the data you collected.
A. How does doubling the height of the cylinder affect its GPE?
B.How does doubling the cylinder’s GPE affect the change in temperature experienced by the water? 
Question: How does the cylinder’s mass affect its gravitational potential energy?
1. Predict: How do you think increasing the cylinder’s mass will affect the final temperature of the water? Explain your prediction
2. Gather data: Make sure the water’s Mass is still set to 1.0 kg and its Temp is 25 °C. Set the cylinder’s 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 cylinder’s GPE for each trial.
3.Compare: Describe any patterns you see and compare your results with the results you got when experimenting with the cylinder’s height in activity A
Question: What factors affect how much the water’s temperature changes when a given amount of heat energy is added to the water? 
1. Form hypotheses: In activity A, you discovered how changing the cylinder’s GPE affects the water’s final temperature. Now consider the following questions:
A. How will changing the water’s initial temperature affect how much the water’s temperature increases when the cylinder is dropped?
B.How will changing the water’s mass affect how much the water’s temperature increases when the cylinder is dropped? 
2.Gather data: Set the cylinder’s 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.
3.Explain: Why was the amount of heat generated the same each time? 
4.Analyze: Use the data you collected to answer the following questions.
A.What was the effect of the initial temperature on the temperature change of the water, and why do you think this happened?
B.What was the effect of doubling the water mass on the temperature change, and why do you think this happened?

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