Specific Heat of Air and Soil
Not all substances warm and cool at the same rate. A characteristic of the substance, called the specific heat, describes how "efficient" the substance heats and cools. The specific heat of air is lower than that of soil; hence, air heats and cools faster than soil. This fact is important to know in the fields of meteorology and agriculture.

Objectives
  1. Given a 24-hour graph of air temperature and soil temperature, the student will be able to calculate the range of air temperatures and the range of soil temperatures measured during the day.
  2. Given a 24-hour graph of air temperature and soil temperature, the student will be able to determine whether the air heats and cools faster than the soil, or vice versa.
  3. The student will be able to explain how the specific heat of a substance affects its heating and cooling rate.
Notes to the teacher
  1. Divide the class into groups of 2 or 3 students.
  2. If you use this lesson as a graphing exercise, provide a table of hourly Mesonet air temperatures (TAIR) and soil temperatures (TB10) for a 24-hour period. If students already know how to graph, you may begin with a completed graph of TAIR and TB10 and skip Procedures #1 and #2 below.
  3. Using a clear day with a temperature range of more than 10°F will lead to easier data interpretation for the students.
PROCEDURE

1. Divide the class into groups of 2 or 3 students.

2. If you use this lesson as a graphing exercise, provide a table of hourly Mesonet air temperatures (TAIR) and soil temperatures (TB10) for a 24-hour period. If students already know how to graph, you may begin with a completed graph of TAIR and TB10 and skip Procedures #1 and #2 below.

3. Using a clear day with a temperature range of more than 10°F will lead to easier data interpretation for the students.

QUESTIONS

1. What do TAIR and TB10 represent?

2. When TAIR increased, what happened to TB10? Why do you think this happens?

3. When TAIR decreased, what happened to TB10? Why do you think this happens?

4. Does TAIR lag or lead TB10? About how long is the lag or lead?

5. Describe what you think would happen to both TAIR and TB10 if a cold front were to pass the Mesonet site.

6. What is the range of air temperatures on your graph? (HINT: Determine the maximum and minimum temperatures and subtract the second from the first.) What is the range of soil temperatures on your graph?

7. What can you deduce about the properties of soil and air from looking at your graphs and your answers above?

APPLICATION

What do the differences in TAIR and TB10 imply for people involved in agriculture?
 PREREQUISITES
  • Basic understanding of conduction
MATERIALS

(Per person):  VOCABULARY

Specific heat

CORE CURRICULUM SKILLS APPLIED IN THIS LESSON
  • Express ideas and opinions orally and in writing.
  • Describe, extend and analyze a wide variety of patterns using tables, graphs and rules.
  • Identify and extend patterns and use experiences and observations to make suppositions.
  • Evaluate results to determine their reasonableness.
  • Predict possible outcomes through simple experiments or simulations.
  • Interpret line, bar and circle graphs.
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