Unit 2: Exploring the Nature of Thermal Phenomena
Question 2.15 What can you learn about science learning and teaching by engaging a friend or family member in learning about thermal phenomena?
- Invite a friend or family member to explore thermal phenomena with you.
- What does this person already know about thermal phenomena in the context of mixing hot and cold water?
- Help this learner do some systems thinking about how energy is conserved when energy flows from hot to cold water.
- Make up a conservation of energy problem and invite your learner to think aloud with you about how to solve it.
- Include the wording of your conservation of energy problem and its mathematical solution.
- Create an environment in which your learner feels comfortable enough to ask questions. Describe what this learner asked and said.
- Also describe what this learner did and found.
- In addition, discuss a NGSS science or engineering practice in which you engaged your learner while learning about thermal phenomena.
- Reflect on what you learn about teaching science through this experience in facilitating science learning.
- Post on the class electronic discussion board. Read your classmates’ postings to learn from their experiences.
Complete this experience in learning and teaching physics before reading the examples of student work about designing and solving thermal math problems.
1. Examples of student work about designing and solving thermal math problems with friends and/or family members
A student engaged her roommate in some qualitative thinking to develop the relationship between masses of hot and cold water and their changes in temperature:
I explored thermal phenomena with my roommate M. Before experimenting, I asked her what she thought would happen when we mixed the hot and cold water and she said that it would become warm water. When I asked why her explanation was just that the cold cools down the hot water while the hot warms up the cold water.
I asked her to try mixing different amounts of water and predict what would happen. We kept all of the results labeled in different cups to compare their temperatures. We did not have a thermometer so we just had to base everything on touch. I asked her to line up the cups from hottest to coldest based on feeling.
M noticed that the hottest had the least amount of cold water in the mixture and the coldest had the least amount of hot water. Since we were not able to measure our temperatures at home, I showed Morgan the data we had collected in class. I did not give her the equation we came up with because I wanted to see where she would go with the information.
She asked me if the temperature changes always need to add up to a specific number. I asked her to try it with different numbers than what we got to see if that was the case. She realized that was wrong because if there is a smaller gap between the temperatures, their temperature differences would be smaller.
M was stumped so I tried having her look at the whole numbers without the decimals. She then realized the big numbers were double the small numbers. After looking at all of the data a little longer she realized that if the amount of hot water was double the cold water, that the temperature change of the cold water would be double that of the hot water.
I then challenged her to imagine what the temperature change would be like if it was 4 parts hot water and 1 part cold water. Immediately M said that the temperature change of the cold water would be 4 times greater than that of the hot.
I asked her if she could come up with an equation and she said it would be hot water divided by cold water would be equal to hot water temperature change divided by cold water temperature change. I asked her to test it with the data. She then realized the second equation would need to be cold temperature change over hot temperature change.
Once she had figured this out I asked her to figure out the temperature change of cold water when 2g of cold water was mixed with 8g of hot water. I also give her the temperature change of the hot water being 5C. She then figured out that the temperature change of the cold water would be 20C.
I used the same examples that had been used in class because I thought it was a good progression of testing understanding. I learned the importance of teaching in steps and building off previous knowledge.
Physics student, Fall 2016
Another student engaged her boyfriend in some interesting thinking about aspects that might affect what happens:
When I asked my boyfriend what happens when you add 4 parts cold water to 2 parts hot water, he said “the temperature increases and the mixture gets warmer, because it’s closer to the cold water. The heat goes into the cold water”. I said, “Right! Because energy transfers from hot water to cold water.”
When I asked him what other factors might affect the transfer of hot water to cold, specifically when you pour the water in, he responded that the container, the air, and the surface the cups are sitting on all could affect the heat transfer.
Then we started talking about how these things may be affected. The amount both containers would take in heat, would matter on what the material it was made out of. M said, “If it was a thermos, it wouldn’t take in much heat, because the heat would be insulated in the cup.”
We also talked about the temperature of the air where you were pouring. Like if it was in Alaska, or Mexico the air surroundings would take in either more or less depending on which.
Next I gave him a word problem on solving for the change in heat of hot water. “What is the change of the hot water, when you have 30 g of hot tea and add 20g of cold water to make it drinkable and the change in temperature of the cold water is 15 degrees.
He was very confused by this complicated problem and thought that we should match the A temperature with A change in temperature and B temp with B change, to get a new temperature of C. But he did not know where to take it from there.
I asked him if he remembered anything about specific heat and showed him the equation to solve for the change in temp of hot water. He solved the algebra easily, but said he probably couldn’t come up with the equation on his own and I agreed that I wasn’t able to come up with it on my own either.
He was on the same page as me about this problem, that the algebra made sense and was easy, but it was the comprehending the bigger picture that was hard to grasp, and thinking up the equation on your own.
I learned that sometimes teachers and learners have the same questions, and that makes it easier to discuss and engage in thorough investigations. Also I learned both having questions lessens the “authoritarian” all knower- teacher type that teachers sometimes possess. We engaged in discussion, using math to solve problems, and analyzed and constructing explanations and designing solutions for the science and engineering practice standards.
Physics student, Fall 2015