Combining Temperatures
I’ve been reading Eleanor Duckworth’s The Having of Wonderful Ideas, and I can’t go a page in the book without reading about an experiment that I want to try on my children. Last night I tried one about combining temperatures on my older sons, who are seven and five years old.
Knowing that my seven-year-old is often right about things, leaving little opportunity for others to be right, I first directed this question at my five-year-old: “Suppose you have two identical pots, each filled with 100-degree water. You pour both into a bigger pot. What’s the temperature of the water now?” My five-year-old son answered without a moment’s hesitation, “They are the same, so the temperature would be the same.”
My seven-year-old son said that the temperature would be 200 degrees. I asked him what the temperature of the human body was. He said 360 degrees. I said, “No, that’s how many degrees are in a circle.” He said 229 degrees. I told him human bodies were around 98.6 degrees, near enough to 100 degrees. We then talked about boiling, which happens at a little above 200 degrees. I then asked him, “What would happen if I drank a glass of 100-degree water? Would that be a good idea or a bad idea?” He said it would be bad idea, so I went and heated up some water to 105 degrees and drank it all in one gulp in front of him. I did not die.
We then talked through the problem some more. I hunted around for similar phenomena to help him understand what happens when you combine temperatures. I started with color: “What happens when you paint red on red?” He said it gets darker and thicker. That metaphor didn’t really help. I paused, not sure where to head next. I gave up on metaphors and went back to temperature.
We talked about water freezing below 32 degrees and ice melting above 32 degrees. “What happens if you put five 10-degree ice cubes next to each other?” He answered that the temperature goes up to 50 degrees. But he paused and pictured the resulting puddle of melted ice cubes, which didn’t make sense to him. “They stay 10 degrees,” he concluded.
Next I asked what would happen if we put an object that was 10 degrees next to an object that was 20 degrees. He said that one object would jump to the temperature of the other. “Which object would change?” I asked. He wasn’t sure. “What happens when you put an ice cube on the counter?” He answered, “It melts.” I asked, “What happens to the counter?” He recalled from his experiences, “It gets cold.” After a brief moment, he concluded, “Both objects would be 15 degrees.”