EXPLORELEARNING GIZMO
Energy Conversion in a System
Name:
Pledge:
Please make sure you login using your username and password. (24 points)
Would you believe that you can increase the temperature of a glass of water simply by stirring it? It's
true! The work that you do in stirring the water is converted into energy in the form of heat, which
increases the water's temperature.
In fact, if you connect a weight to a water-stirring device, you can even heat up a glass of water a tiny
bit just by dropping the weight.
James Prescott Joule, an English brewer in the 1800s, used exactly that method to demonstrate that
gravitational potential energy can be converted directly into heat energy. One of the challenges that
Joule faced was measuring the tiny temperature changes that occurred as a result of his paddles
whirling in a container of water. He claimed to have perfected a method of measuring temperature
changes to an accuracy of 1/200 of a degree Fahrenheit.
Converting Gravitational Potential Energy to Heat Energy
Energy can be converted from one form to another. In this activity, the gravitational potential energy of
the cylinder will be converted to heat energy of the water.
1. In the Gizmotm set the mass of the water to 1.0 kg and the initial temperature of the water to
10°C. Set the mass of the cylinder to 5.0 kg and its height to 400 m. (To quickly set a slider to a
value, type the value in the field to the right of the slider, and press Enter.) Click Play ( ).
1. As the cylinder falls, what happens to the temperature of the water?
2. Click the TABLE tab. What was the final temperature of the water?
did the temperature of the water increase?
By how much
2. Click Reset ( ). Leave the settings the same as in the initial experiment (mass of water = 1.0
kg; initial temperature = 10°C; mass of cylinder = 5.0 kg) but set the height to 800 m rather
than 400 m.
1. How does this change affect the initial gravitational potential energy (PE) of the cylinder?
(Remember, PE = mgh, where m is the mass of the object, g is the acceleration due to
gravity, and h is the object's height.)
2. Click Play. By how much does the water temperature increase?
compare to the temperature increase from the previous trial?
How does this
3. You should have seen that doubling the height of the cylinder also doubles the
temperature change in the water. What do you think would happen if you triple the
height? To find out, perform two experiments in the Gizmo. First use height = 200 m,
and then use height = 600 m.
4. Make a general statement about the relationship between the initial height of the
cylinder and the temperature increase when other factors (like the mass of the water and
the mass of the cylinder) remain constant.
5. Click the GRAPH tab. Be sure that Temperature is selected from the dropdown menu. Is
the graph of Temperature vs Height a line or a curve?
Is its slope positive or
negative?
Explain how these characteristics of the graph agree with your
statement relating the temperature change to the initial height of the cylinder.
3. Click Reset. Return the settings to the same values as in the initial experiment (mass of water =
1.0 kg; initial temperature = 10°C; height = 400 m) but this time set the mass of the cylinder to
10.0 kg rather than 5.0 kg.
1. How does this change affect the initial gravitational potential energy of the cylinder
compared to the original trial?
Predict what the final temperature will be in this
case.
Use the Gizmo to check your prediction.
2. What would you expect the final temperature of the water to be if you were to double
the mass AND the height of the cylinder (compared to the original experiment)?
Test your hypothesis using the Gizmo.
Factors Relating Heat Energy and Temperature
In this activity, you will explore factors that affect the size of the temperature increase that occurs when
a given amount of heat energy is added to a substance.
1. In the Gizmo, set the mass of the water to 0.6 kg and its initial temperature to 15°C. Set the mass
of the cylinder to 10.0 kg and its height to 800 m. Click Play.
1. Click TABLE. What is the final temperature of the water?
temperature of the water increase?
By how much did the
2. Click Reset. Repeat the experiment with the initial temperature set to 30°C, but with all
of the other values the same. What was the final temperature in this case?
By
what amount did the temperature increase?
3. How does the initial temperature affect the amount by which the temperature increases?
2. Click Reset. Return the settings to their original values for this activity (initial temperature =
15°C; mass of the cylinder = 10.0 kg; height of the cylinder = 800 m), but this time double the
mass of the water to 1.2 kg. Then click Play.
1. By how much does the temperature increase in this case?
to the increase when the mass of the water was only 0.6 kg?
How does this compare
2. Click Reset. Leave all of the settings the same except for the mass of the water. Set the
mass of the water to 0.9 kg. What do you expect the final temperature to be in this case?
Click Play and check your answer. What did you find?
3. Click Reset one more time. Return the variables to the original values for this activity
(mass of water = 0.6 kg; initial temperature of water = 15°C; mass of cylinder = 10.0 kg;
height of cylinder = 800 m). Refer back to how much the temperature increased in this
case. What would you expect the final temperature to be if you were to increase the mass
of the water to 1.2 kg, decrease the mass of the cylinder to 5.0 kg, and reduce the height
of the cylinder to 400 m?
Use the Gizmo to check your hypothesis.