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Lesson Plan: Soil Heat Capacity
Subject: Earth and Space / soils / heat capacity
Classtime: 100 minutes
Grade Level: 8-12

Materials/Technology:

  • bunsen burner, gas hose, and igniter
  • 600 ml beaker
  • Celsius Lab Thermometers or CBL with temperature probe, two for each group
  • supply of soil
  • supply of clean fine sand
  • beaker ring, ringstand, wire mesh, test tube clamp, spatula, and beaker tongs
  • test tube, size 18x150 mm
  • 100-ml beaker
  • triple beam scale or other mass measuring device accurate to +-.1g
  • 3 Styrofoam cups, 2 the same size and 1 large enough to act as a lid for the smaller cups. (Cut a hole in bottom of large cup to allow thermometer or temperature probe access to water in calorimeter.)

Safety, Handling, Disposal:

Students are expected to have proper lab technique for: safely using the Bunsen burner, boiling and disposing of water, proper care of glassware, sensitive measuring devices and other lab equipment. Pour hot water down the sink; the sand and soil may be discarded in the regular trash or dried and re-used if the instructor wishes.

Learner Outcomes: Students should be able to:

  • Determine the specific heat for topsoil and sand.Properly use lab equipment to collect data needed to determine specific heats.
  • Use formulas and calculations to quantify the specific heat for both substances.
  • Manipulate formulas to solve specific unknown values.

Problem/Purpose:

To experimentally determine the specific heat of topsoil and sand.

Background:

Heat is a form of energy and can be expressed in units of the Joule(J). One Joule is equivalent to a force (in Newtons) times a distance (in meters). Therefore, a Joule is the same as a Newton * meter.

The specific heat of a substance is defined as the amount of energy necessary to raise the temperature of 1 gram of the substance by 1 degree Celsius. The unit of specific heat is J/g*C. For water, specific heat = 4.18 J/g*C. Specific heat, heat and temperature are related to each other by the following formula: heat =(mass) x (specific heat) x (change in temperature). Water has a large specific heat, whereas metals have a small specific heat. Metals heat up (and cool down) fast; water heats up (and cools down) slow.

Heat, symbolically, is represented as: q = m* c* "T ; where q = heat lost or gained, m = mass in grams, c = specific heat in J/g*C , and "T = the final temperature minus the initial temperature. The use of a calorimeter is essential in determining the specific heat of substances.

A calorimeter is a device used to measure the heat liberated by a substance or object. It consists of a highly insulated container with a known quantity of water. The insulation prevents heat from being gained or lost by the water in the calorimeter to the surroundings. You will use a calorimeter, with a known amount of water in it, to measure the heat liberated from clean fine sand and topsoil. By observing the temperature rise when those heated substances are placed in cool water, and the formula above, students will be able to calculate the specific heat of each substance.

Your calorimeter will consist of two Styrofoam cups, one inside the other (as if to stack). A second larger Styrofoam cup will be placed over the two. This will be the lid (the setup should look like the two large ends of ice cream cones placed together with no ice cream in between).

The known value of the specific heat of water will be used to calculate the specific heat of each substance. Remember, specific heat of water = 4.18 J/g*C.

Vocabulary List: Here.

Hypothesis:

Example: The topsoil will have the same specific heat as the sand.

Procedure:

  1. Set a 600-ml beaker three-fourths full of tap water on a ring stand with wire screen and heat with a Bunsen burner to boiling.

  2. Add exactly 70 ml of water at room temperature to your calorimeter (Styrofoam cups). REMEMBER: 70 ml of water has a mass of 70 g.

  3. Place the 18x150 mm test tube on the balance and determine the mass to the nearest tenth of a gram. Record on the data table.

  4. Fill the test tube about half-full of sand. Determine the mass of the test tube and sand and record on the data table.

  5. Pour the sand into the clean dry 100-ml beaker.

  6. Place the thermometer or the probe into the test tube. Do not allow it to touch the bottom or the sides of the test tube.

  7. Pour all the sand from the beaker into the test tube so the temperature measuring device is completely surrounded by the sand. BE CAREFUL not to spill any. If spills occur, pour all the sand into the original container, and return to step 4.

  8. Place this tube in the boiling water bath using the test tube clamp and ringstand. Allow it to heat for ten full minutes after the water returns to boiling. The substance in the test tube should be completely below the level of the boiling water during heating. Record this temperature on the data table.

  9. Measure and record the temperature of the 70 mls of water in the Styrofoam cup. This is the initial temperature of the water in the calorimeter. |

  10. After 10 minutes of heating, carefully remove the test tube from the boiling water and pour the substance into the cup. Be careful not to splash water from the cup. Quickly cover the cup and insert the thermometer. Swirl the contents. Observe the rise in temperature of the contents.

  11. Record the highest temperature attained by the thermometer in the calorimeter. This is the final temperature of the substance and of the water inside.

  12. Dispose of the material in the calorimeter as the teacher instructs. Rinse and dry the calorimeter and test tube, then repeat from step 4 with the topsoil.

Calculations on separate piece of paper first calculate the heat gained by the water (q) in the calorimeter using: q = m* c* "T. (For the water use the mass of water, the specific heat of water and the temperature change of the water).

The Law of Conservation of Energy requires that the heat gained by the water must equal the heat lost by the substance, so q of the substance = q of the water.

Use the formula again: q = m* c* "T, but this time insert the mass of the substance, the temperature change of the substance and q substance. Solve for c, the specific heat of the substance. You will need to do all of this for both the sand and the topsoil. There will be a total of four calculations. Two (sand and topsoil) using: q = m* c* "T, and two (sand and topsoil) using: q /(m * "T) = c.

Advance Teacher Preparation:

It is strongly recommended that teachers complete this lab themselves before attempting it with their students. Many mistakes/accidents can be avoided by this simple strategy.

Each group will need the Styrofoam cups described above. Two thermometers for each group is needed. One for the substance and one for use in the calorimeter.

Results/Analysis:

SPECIFIC HEAT

Name_____________________

Section____________________

Date_____________________

Instructor__________________

1. Volume of water in calorimeter ______________ml.

2. Mass of water __________g

3. Mass of test tube __________g

4. Mass of test tube and sand ___________________g

5. Mass of test tube and topsoil ___________________g

6. Mass of sand ___________________g

7. Mass of topsoil ___________________g

8. Temperature of sand after 10 min in boiling water ___________________ C

9. Initial temperature of water in calorimeter (before sand added)_____________ C

10. Final temperature of water in calorimeter (after sand added)_____________ C

11. Change in temperature of water ( "T) ___________________ C

12. Temperature of topsoil after 10 min. in boiling water ___________________ C

13. Initial temperature of water in calorimeter (before topsoil added)_____________ C

14. Final temperature of water in calorimeter (after topsoil added)_____________ C

15. Change in temperature of water ( "T) ____________ C

16. Heat gained by water in calorimeter ____________J

Use: q = m* c* "T

17. Change in temperature of sand ( "T) ____________ C

18. Heat (q) lost by substance = Heat (q) gained by water (answer to 16) ____________J

19. Specific heat of sand ________________J / g*C

(calculate by: q /(m * "T) = c)

20. Change in temperature of topsoil ( "T) __________ C

21. Specific heat of topsoil ________________J / g*C

(calculate by: q /(m * "T) = c)

Conclusions:

The conclusion should include calculated values for both the sand and the topsoil and show which heats/cools quickest based on these numbers. Speculation as to why these substances are different should be encouraged.

Assessments:

  • A student heated a metal object weighing 40.0 grams to 100C. She placed this metal into a calorimeter which contained 175 g of water at 20.0C. The maximum temperature that the water and metal in the calorimeter reached was 22.2C. What is the specific heat of the metal?
  • A metal with a mass of 28 grams is heated to 94C. This metal is placed into a calorimeter which contains 85 ml of water at 21.3C. The maximum temperature the water and metal in the calorimeter reached was 25.7C. What is the specific heat of this object?
  • A Joule is a measure of work. What is a Joule equal to?
  • If 4.18 Joules of heat energy are added to 1 gram of water, how much will this raise the temperature of the water?
  • What do the symbols "T mean? How do you find this quantity?
  • One substance has a specific heat of 1.4 J/g*C, another has a specific heat of 5.7 J/g*C. If you could shape each substance into a cooking pan, which substance would you choose to construct the pan? Why?
  • How might plants respond to different soils specific heats? Use the results of this lab to guide your response.

Integration: Mathematics, lab techniques, English, Physics.

Reflections:
Share your thoughts on this lesson with the NTEN team.

Please send an e-mail to Patti Harrison.

Extensions:

  • Since specific heat is a physical property of specific substances, use this lab to determine the specific heats of metal elements. This is the most common use of specific heat measurements.
  • Have students use dissecting microscopes to discover: the size of the particles in the sand verses the topsoil and the minerals that make up each. Use this information to hypothesize the cause for the differences in specific heats of the two substances.

References/Resources:

URLs

http://fermi.bgsu.edu/~stoner/p201/heat/

http://www2.austin.cc.tx.us/rvsmthsc/chem/book.htm

Credits
Contributing Teacher: The idea for soil specific heat: Pasquale Puleo. Model for lab procedure: Peggy Croshaw
NTEN Course: The Dirty Dozen
Instructor: James W. Bauder
Developing Team:
T.L. Buck Buchanan, Patti Harrison, Don Samuelson, John Usher, Don Wilson
HTML Programmers: Tyson N. Trebesch, Ryan Huddleston, Andy Tomascak, Ching-Kwong Chia

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Comments: pattih@montana.edu

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