WINTER HOT SPOTS

PURPOSE:  To investigate heat transfer in the winter environment.

MATERIALS: Suitable dress for winter, camera and print film, pencil, notebook or index cards, felt-tipped marker, old ski or other outdoor magazines (optional).  Drawing materials may be substituted.

INTRODUCTION:  Comments on nature in winter usually lead to a simple, one word description:  cold.  To a casual observer, the winter scene appears to be a frozen, white, unchanging wasteland.

In reality, dynamic processes are always occurring in the winter environment.  Heat (what little there may be) is being exchanged by conduction, convection, and radiation.  Warm spots can be found by locating areas where snow melts first.  Frost spots form on the coldest objects outdoors.  These nearly opposite categories often occur at the same time in different places in the winter environment.

In this investigation, you will look closely at the winter environment.  Using the basic principles of heat transfer, you will be able to explain many of the observations you make.  When you complete this activity, you may never look at winter the same way again!

PREDICTION: Use what you know about natural and manmade sources of heat in the winter environment to make a prediction.

1.  Where do you think you will find evidence of warm spots and frost spots in the winter environment?

PROCEDURE: 

A.  Photograph or sketch as many examples of warm spots and frost spots as possible:

B.  Look through old ski or outdoor magazines for other examples of hot spots and first frost.  Describe the heat transfer mechanism involved as above.

C.  Separate your pictures into two groups: those representing warm spots and those showing examples of frost spots.

D.  Neatly display each picture.  Label each with the information from your notebook or index cards. Give a brief description and explanation of what is occurring in the picture.

DISCUSSION:

2. Are most warm spots light or dark-colored?  Explain your answer.

3. Why is there often a depression in the snow at the base of a leafless tree?

4. What is the relationship between warm spots and compass direction?

5. Why does the snow melt unevenly around the base of a tree?

6. What evidence did you find that the sides and roof of some buildings are warm spots?

7. A house with very few icicles present is sometimes found beside a similar house with many large icicles.  Give one possible explanation for this observation.

8. Explain why dirty snow melts faster than the same amount of clean snow.

9. In winter, why is the temperature often higher near an unfrozen lake than further inland?

10. Why are objects that are not in direct contact with the ground (such as the center of a bridge or the body of an automobile) more likely to have frost?