What is Room Temperature? (~3 hrs.)
Imagine this scenario: You're sitting by a sunny window in your kitchen reading a book and enjoying the warmth of the afternoon sun. You come back to the same spot later in the evening to pick up your book and you remark that it seems like the coldest place in the room, although your thermostat has been set at the same 20°C all day. How do you define room temperature? How much does the temperature in one place vary over time?
Begin by exploring the range of temperature values that you might find in your kitchen.
The term system refers to a well-defined group of atoms, molecules, particles, or objects. When scientists study heat transfer and temperature change, they first define a system of study. You may have a large drafty kitchen, or a small sunny kitchen. For this exploration, the system is your kitchen. (If you don’t have a kitchen, use your friend’s, or even your school’s).
In your journal, sketch a map of your kitchen. Use your senses to guide you as you explore. Where is the temperature highest and where is it lowest? (E.g., near the ceiling, behind the refrigerator, in the freezer, the warm tap water, you). Annotate the map, describing the different temperatures you feel. How much variation is there?
Select eight locations where you’re curious about the temperature, or where you think you’ll find the highest and lowest values. At each location, note the temperature in degrees Celsius that you think you'll find when you measure.
Tape the thermometers from your kit to each of the 8 locations you selected. Record the temperatures in degrees Celsius on your annotated kitchen map. NOTE: Don’t place thermometers where someone can accidentally step on them. Don’t put a thermometer in a place (like the oven) that may exceed the maximum temperature on the thermometer.
Any surprises? What pattern do you see? How might you explain the variation in temperature? This is an exploration - no need to post your findings.
Establish Familiar, Personal Benchmarks of Temperature in Degrees Celsius
As you work through this course, develop a list of personal temperature benchmarks that will help you estimate the temperature of objects or places in the kitchen and beyond.
Begin now! For example, water freezes at 0°C and boils at 100°C; body temperature is 37°C. What other benchmarks have you found, for example, room temperature is about 22°C?
Choose one place to investigate
Now that you've explored the whole kitchen at one particular moment in time, select a place that interests you to investigate temperature change over a period of time.
- How does the temperature vary near the window where the afternoon sun shines?
- Does the temperature near the dinner table increase when several people gather there to eat?
- Does the temperature in your freezer rise every time you open the freezer door? How about the air around the freezer?
NOTE: If you don’t have a laptop or your computer isn’t in your kitchen, investigate a system that is near to your computer.
If you were to measure the temperature in the area you chose to study over several minutes, hours, or overnight, how would it vary?
Before you investigate, create a diagram of your system. Annotate it with a prediction for temperature changes in degrees Celsius over a specified time period, and a rationale for your prediction.
C. Collect Data
Place your temperature probe in the area you chose to study, adjust the time range as needed (see Tips for Using Temperature Probes) and record the temperature over time. (You can just leave the investigation to run on its own if you prefer, once you’re sure your computer is generating a graph.)
Print out your graph of temperature vs. time and add it to your journal. See Tips on Using Temperature Probes to find out how to save Logger Lite files so that you can include them in your post.
The PhET Gas Properties model, developed at the University of Colorado at Boulder, allows you to ask questions and make predictions about what might happen to a gas under a variety of conditions. For example, you can ask what happens if you change the number of particles, add heavy or light species particles, or change the temperature.
Use the PhET Gas Properties model to test your ideas. As you work, take notes in your journal.
Track individual particles:
- Track two different "heavy species" particles, and compare their speed.
- Track a "light species" particle and a "heavy species" particle and compare their speed.
Compare the graphs showing speed and kinetic energy:
- at 2 different temperatures
- for heavy vs. light species.
Tips for Using the PhET Gas Properties Model
- Add particles by using the up and down arrows for "Heavy Species" and "Light Species" in the "Gas in Chamber" box. Compare behavior of 100 heavy particles, 100 light particles, and 100 of each.
- Raise or lower the temperature by moving the slider in the "Heat Control" box.
- Record patterns in the speed and kinetic energy histograms for the particles. Click on "Measurement tools" and select "energy histograms." On the Particle Statistics window that opens, select "More details."
N.B. The kinetic energy (KE) of an object is its energy of motion. It depends on mass (m) and speed (v=velocity). It is equal to half the mass multiplied by the speed squared.
Kinetic energy = 1/2 mass x speed2
D. Reason from Evidence
Use your data (temperature graph and molecular model notes) as evidence to determine how well your prediction and rationale are supported.
- Describe in words how the temperature in the system you investigated changed over time. Identify the starting temperature, the final temperature, and patterns of temperature change. (Read Analyzing Temperature Graphs) to help you identify common patterns of temperature change.)
- Think of the kitchen system you investigated in terms of the PhET gas model. Explain the temperature variation you found on a particle scale.
Read about temperature on pages 290-292 in Conceptual Physics, Chapter 15. Add any new insights or questions to your explanation of temperature variation.
E. Your Temperature Story
Use the notes and diagrams from your investigation to write the story of temperature change in the location you investigated. In your report,
- Describe your investigation, and the location that you chose. Tell us what captured your attention about that place.
- Describe the temperature variations you observed. Use evidence from your investigation on a macroscopic scale using temperature probes and your investigation on a particle scale using the PhET Gas Model.
By Wednesday, post your temperature story in the Forum. Attach your temperature vs. time graph to your post; your data may raise new insights or questions for your group to discuss.
You’ve each studied a different system and have a different story to tell. Between Wednesday and Saturday you'll have a chance to compare your stories and your explanations.