Unit 2: Exploring the Nature of Thermal Phenomena

# IV. Using Central Ideas about Thermal Phenomena to Explain an Intriguing Phenomenon

One aspect of the nature of science is its use of central ideas based on evidence in developing explanations of intriguing phenomena. The central idea that materials differ in the property of thermal conductivity can explain why some materials feel cooler than others even though they are the same temperature.

### A. Applying the property of thermal conductivity in an everyday context

##### Question 2.5 Why do the metal legs of a chair feel cooler than its plastic seat?
• Use the central idea about thermal conductivity to explain this observation.
• Also engage a friend or family member in learning about such thermal phenomena.

#### 1. Example of student work explaining an intriguing thermal phenomenon

After discussing the difference between heat and temperature, a student wrote:

The ideas above can help explain why metal parts of a chair feel colder than the plastic seat even though both parts of the chair have been in the same room for the same amount of time. One important idea to remember is that the metal part and the plastic part are the same temperature, regardless of how they feel. The metal part of the chair is a conductor so the heat from our bodies transfers quickly to the metal, leaving our hand feeling cold. However, plastic is not as conductive; the heat from our bodies takes longer to transfer to the plastic so our hand feels warmer.

I invited my friend to explore thermal phenomena with me. I engaged my friend in thinking about the difference between heat and temperature by adapting the activity we did in class with materials that I had in my house. I provided her with a metal spatula, a wooden spoon, and a Styrofoam coffee cup. I asked her to feel each of the objects and rank these materials by temperature and to roughly estimate what the temperature of each object was. She, like many of us in class, gave a clear ranking and suggested that the temperatures of each object were dramatically different.

I then explained, because I did not have a thermometer to prove it, that each of the materials was the same temperature. She looked at me puzzled and bluntly asked why they felt so obviously different. I explained to her, like it is stated above, that the materials act as conductors, some better than others, and that the rate the heat is transferred determines how it feels to us.