Materials Included In Kit

Additional Materials Required

Safety Precautions

Caution students that the lights and lamps may become very hot during the experiment. Wear heat-resistant gloves when handling hot materials. Sand may be irritating to the eyes. Wear safety glasses. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The water may be disposed of down the drain according to Flinn Suggested Disposal Method #26b. All other materials may be stored for future use or disposed of in the common garbage according to Flinn Suggested Disposal Method #26a.

Lab Hints

• Enough materials are provided in this kit for 30 students working in groups of 3 or for 10 groups of students. This laboratory activity can reasonably be completed in one 50-minute class period. The prelaboratory assignment may be completed before coming to lab, and the data compilation and calculations may be completed the day after the lab.
• Local soils may have a different specific heat than the dark soil provided with this kit. The amount of moisture in the soils will affect the specific heat.
• The infrared lamp and reflector (Flinn Catalog No. AP5372) worked well during testing. Typical fluorescent classroom light will not provide enough infrared radiation to significantly heat the material used in this activity.
• Air conditioning can affect the results of this experiment.

Teacher Tips

• Specific heat of common geological materials (joule/gram °C)

  Air, room conditions—1.012
  Asphalt—0.920
  Brick—0.840
  Concrete—0.880
  Glass—0.837
  Iron/steel—0.452
  Marble—0.858
  Sand—0.835
  Soil—1.046
  Water, liquid, 25 °C—4.183
  Water, solid, 0 °C—2.114
  Wood—1.674

Further Extensions

Alignment with AP^® Environmental Science Topics and Scoring Components

Topic: Earth Systems and Resources. The Atmosphere (Composition; structure; weather and climate; atmospheric circulation and the Coriolis Effect; atmosphere-ocean interactions; ENSO).
Scoring Component: 1-Earth Systems, Atmosphere.

Answers to Prelab Questions

1. Using the information in the Background section, explain why the temperature measured on a thermometer is lower in the shade than in the sunny area adjacent to the shadow.

   Shade is cooler due to the amount of solar radiation that is absorbed and reflected away from the shady area by the item casting the shadow.

Sample Data

Data Table 1

Answers to Questions

1. On a separate piece of paper, graph the results obtained when the materials were heated by plotting the time in seconds on the x-axis versus the temperature in Celsius on the y-axis for each material. Plot all four samples on the same graph. Use a different-shaped or a different-color data point for each material.
   {10844_Answers_Figure_2}
2. Which material used in this activity heated up the fastest? Explain.

   The black sand heated the fastest. Within 90 seconds its temperature had increased by more than 5 °C. Black sand has a low albedo, absorbing most of the incoming radiation.

3. Determine the maximum temperature change (ΔT) for each material by subtracting the initial temperature (T₀) from the final temperature measured after 600 seconds (T₆₀₀). Record the results in the table.
4. Calculate the change in temperature per gram of material by dividing ΔT by the mass of material used and enter the results in the table.
5. Using the graph, determine which material used in this activity has the highest specific heat. Explain.

   The water has the highest specific heat because the temperature increased by the least amount per gram. All of the samples should have received the same amount of heat from the lamp. Specific heat is the amount of energy required to heat one gram of material by 1 °C. Water requires the greatest amount of energy to heat one gram by 1 °C.

6. Using the results of this lab, explain why there is a greater range of temperatures in the United States throughout the year in the Midwest compared to the coastal areas.

   Coastal areas are very close to large bodies of water which have a high specific heat and therefore moderate the climate.

References

U.S. Department of Commerce (DOC), National Oceanic & Atmospheric Administration (NOAA), National Environmental Satellite, Data, and Information Services (NESDIS), National Climatic Data Center (NCDC), http://wwwncdc.noaa.gov/oa/globalextremes.html#hightemp (Accessed June 2007)

U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Atmospheric Radiation Measurement (ARM) http://education.arm.gov/teacherlounge/background/differentclimates.stm (Accessed June 2007)

http://www.answers.com/topics/specific-heat-capacity?cat=technology (Accessed June 2007)

Introduction

The temperature of the Earth’s surface varies from a low of –129 °F in the vast ice domain of Antarctica to a high of 136 °F in the desert of Africa. How does the composition of the Earth in a given region affect the temperatures in that region?

Concepts

• Albedo
• Solar radiation
• Specific heat

Background

Temperature varies across the surface of the Earth for several reasons. Two important factors that determine the local temperature are the intensity of solar radiation and the surface properties of the area. The intensity of solar radiation is largely a function of the angle that the Sun’s rays strike the Earth’s surface. If the Sun is positioned directly overhead the rays strike the Earth in a concentrated area. If the Sun is at an angle overhead, the incoming rays strike the Earth’s surface at an angle and the rays spread out over a larger surface area, reducing the intensity of the solar radiation.

The intensity of solar radiation is also determined by the number of hours of daylight per day over a particular area. Equatorial areas have about twelve hours of daylight every day with the angle of the Sun between 66.5° and 90° overhead. The North Pole receives maximum daylight on the summer solstice when the Sun is at 23.5° the whole day (the Sun does not set). Around the winter solstice the Sun never rises at the North Pole and there is no daylight.

The altitude (height) of a location also affects the intensity of solar radiation. The ground receives solar radiation and then heats the air above it by long-wave radiation, conduction, and convection. The temperature decreases with height in the troposphere at a rate of 6.5 °C for every 1000 meters. This is why some high altitude areas near the Equator—such as Papua, New Guinea—have glaciers.

The type of surface also affects the temperature of different areas of the Earth. The amount that a surface reflects the solar rays, called albedo, plays an important role in temperatures. Albedo is the fraction of incoming solar radiation at a surface—whether land or cloud top—that is reflected by that surface. Surfaces with a high albedo reflect more incident radiation than less reflective surfaces. Cloud cover is an example of this. The top of thick clouds reflect incoming solar radiation during daylight keeping the ground cooler. This is why clouds cast shadows. The bottoms of thick clouds reflect heat radiation from the ground at night, keeping the area warmer. Beaches may reflect up to half of all the solar energy received, particularly if they are composed of white sand. In contrast, dark surfaces such as forests will absorb most of the incoming radiation and temperatures above them will be higher than light-colored surfaces.

In addition to albedo, the composition of the surface causes differences in temperature. All substances are able to heat up or cool down at a specific rate based on their specific heat. Specific heat is the amount of energy required to heat a specific mass of a substance by 1 °C. The specific heat of water is 4.186 joule/gram °C, which is higher than most other substances. Consequently, water plays a significant role in temperature regulation. The higher the specific heat the more energy will be required to heat the substance to a given temperature. In general, water heats more slowly and also cools more slowly than land. This means that land and air have lower specific heats than water. In warm months the air over land near large areas of water, like oceans, remains cooler during the day than air over land that is not near large bodies of water, due to the specific heat of the nearby water slowly absorbing heat. At night, when the area is not exposed to solar radiation, the water slowly releases its heat, thus raising the air temperature.

Experiment Overview

The purpose of this experiment is to compare how similar amounts of infrared radiation affect the temperature of geological materials.

Materials

Prelab Questions

1. Using the information presented in the Background section, explain why the temperature measured in the shade will be lower than the temperature measured in the sunny area adjacent to the shadow.

Safety Precautions

Use extreme caution while using heating equipment in this activity. The lamp and bulb may become very hot. Do not leave lamps unattended. Wear heat-resistant gloves. Sand grains can scratch eyes. Wear safety glasses. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.

Procedure

1. Measure the mass of an empty Petri dish on the balance. Record the mass of a Petri dish in Data Table 1, row a, under water on the Specific Heat Worksheet.
2. Fill the Petri dish to just below the brim with water (about 70 mL) and measure the combined mass of the Petri dish and water. Record the mass in Data Table 1, row b, on the Specific Heat Worksheet.
3. Subtract the mass of the Petri dish with water from the mass of the empty Petri dish and record the mass of the water in Data Table 1, row c, on the worksheet.
4. Place a thermometer under the surface of the water in the Petri dish. Note: The bulb of the thermometer must remain under the surface of the water. The exposed end of the thermometer may need to be placed on paper towels to prevent it from tipping out of the Petri dish.
5. Repeat steps 1–5 three more times using the black sand, white sand and soil, respectively.
6. Arrange the four Petri dishes in a square pattern underneath a light source or infrared heat lamp (see Figure 1).
   {10844_Procedure_Figure_1}
7. Lower the light source or infrared heat lamp until it is about one inch above the surface of the Petri dishes. Make sure that the Petri dishes are being exposed to equal amounts of light.
8. Measure the temperature of each substance in the Petri dishes every 30 seconds for 10 minutes, and record the temperatures in Data Table 2 on the Specific Heat Worksheet.
9. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF

10844_Student1.pdf