Specific Heat and Insulation
This activity expands the student's knowledge of how temperature changes between air and soil. It also examines how natural grass cover insulates the effects of the sun's direct radiation.

Objectives
  1. Given a 24-hour graph of soil temperature, the student will be able to calculate the range of soil temperatures measured during the day.
  2. Given a 24-hour graph of 10-cm soil temperature under both bare soil and natural sod, the student will be able to determine which soil cover (bare or sod) allows for faster heating and cooling rates.
  3. The student will be able to explain how the specific heat of a substance affects its heating and cooling rate.
  4. The student will be able to explain how the insulation 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), 10-cm bare soil temperatures (TB10), and 10-cm soil temperatures under sod (TS10) for a 24-hour period. If students already know how to graph, you may begin with a completed graph of TAIR, TB10, and TS10 and skip Procedures #1 and #2 below. In addition, students can simply add TB10 to the graph from "Specific Heat of Air and Soil".
  3. Using a clear day with a temperature range of more than 10°F will lead to easier data interpretation for the students. It is best to do this activity in the late spring through fall, when there is substantial amount of sod cover on the ground.
PROCEDURE

1. Plot Mesonet air temperatures (TAIR) versus time and soil temperatures (TS10 and TB10) versus time on the graph paper. Use different colors to designate TAIR, TS10, and TB10.

2. Label your graph properly.

3. Compare the information plotted on your graph to answer the following questions.

ANALYSIS

1. What do TAIR, TS10, and TB10 represent?

2. When TAIR changes, does TS10 change more or less than TB10? Why do you think this happens?

3. Does TS10 lag or lead TB10 as the air temperature changes?

4. How do you think TS10 and TB10 would compare at 20 cm? 5 cm? Why?

5. What is the range of 10-cm soil temperatures (under sod) on your graph? (HINT: Determine the maximum and minimum temperatures and subtract the second from the first.) What is the range of 10-cm bare soil temperatures (TB10) on your graph?

6. Using the information from your answers above, would you plant a seed in the spring under bare soil or sod covered soil? Why?		 PREREQUISITES
  • Basic understanding of conduction and specific heat
MATERIALS

(Per person):  VOCABULARY

Insulation
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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