Name ___________________ Modeling the Melting of Ice In our exploration of the tiles, we ended with a macroscopic model of thermal energy transfer as well as a model that explained our observations in terms of the movement and interaction between the particles. 1. Now, we will think about the process of the melting of the ice. Using the model that you came up with previously, describe how the particles will be moving in the ice as kinetic energy continues to be transferred from the tile to the ice.
2. If the particles are behaving in the way that you have described above, how will the temperature of the ice change as it melts?
3. Test your prediction by measuring the temperature of the ice as it melts using an IR thermometer. Record your observations here.
4. Do your observations support your model? Explain how your observations fit with your model and modify your model to better incorporate any observations that contradict it. Be prepared to share your group’s model with the class.
American Association of Chemistry Teachers
|1-291
1
5. Suppose a piece of ice is taken out of a very cold freezer (-40oC) and placed into a beaker. Then it is placed on a hot plate and heated, transferring energy to the ice at a constant rate. The temperature is taken until the ice has melted. What would the graph of Temperature vs Time look like? Make your prediction on the graph provided below.
Your instructor will provide you with a graph of Temperature vs Time. 6. In the circles below, draw particle models for the water at each section of the graph.
American Association of Chemistry Teachers
|1-291
2
7. Using the model that you developed, what can you say about the kinetic energy of the particles during each portion of the graph? During each portion of the graph, how is the behavior of the particles changing as energy is added?
8. Some of the information from the graph suggests that the added energy does not only change the movement (kinetic energy) of the particles. What other particle changes are being caused by the addition of energy?
9. How do the particles of a substance change during the phase change? What role do you think energy plays in the change?
10. As a group, return to the model of the melting ice from question 1. Modify your model to incorporate any new understandings of the role energy plays in phase changes.
11. Now that we’ve come to a consensus as a class, let’s think about how we can model the changes in energy visually and graphically. a. What objects are exchanging energy in this situation? List the objects that are exchanging energy and connect objects that are exchanging energy with a line.
American Association of Chemistry Teachers
|1-291
3
b. The diagram on the right (known as a schema) represents some of the key objects in this situation. The dashed circle separates the system (objects we’re studying) from the surroundings (everything else). Draw arrows at the end of each solid line indicating the direction of energy transfer between objects. 12. Use the chart below to represent the initial distribution of energy and how the energy flows at each stage in the process.
A
B
C
D
American Association of Chemistry Teachers
|1-291
4
13. Now, let’s see if we can apply our model to the reverse process. Consider liquid water being placed into a cold freezer. How will the behavior of the particles change over time? How will energy be exchanged over time? Use the diagrams provided below to construct your model of the process. Liquid
Freezing
Solid
American Association of Chemistry Teachers
|1-291
5
