Determining the Density, pH and Water Content of Various Area Soils
Summary
SUMMARY: In this chemistry field lab, students will determine the density, pH and water content of 4 types of soil; 1) prairie soil, 2) transition soil, (where the prairie meets the trees) 3) woods soil, and 4) riverbed soil at various locations in and around the Fergus Falls area. Students will compare class data and write a lab report describing their results. A detailed lab report format will be provided. Students will also analyze their findings and report on the various differences and similarities found in their soil samples.
CollapseLearning Goals
LEARNING GOALS. This activity is designed for students to: 1) properly collect, dry and determine a soil's density, pH and water content; 2) question why various soil samples are different; 3) graph mass vs. volume for the four soil samples and interpret their results.
KEY CONCEPTS: 1) Define mass, volume, density, pH, and water content; 2) Create a graph that reveals patterns in collected data. 3) Explain the derived units for density.
KEY CONCEPTS: 1) Define mass, volume, density, pH, and water content; 2) Create a graph that reveals patterns in collected data. 3) Explain the derived units for density.
Context for Use
This activity works best with 24 students or less in grades 6 through 12 in groups of two. After a lesson on density, this activity relates nicely with the subject and helps achieve the educational outcomes. It may include a field trip to areas where the four different types of soil are found. (The teacher may also bring various samples to school.) A drying oven is helpful to have (to hasten soil drying time) as well as inexpensive pH meters. This is an excellent lesson to help students understand simple graphing techniques as well as hands on use of a computer with an Excel program. This activity is situated at the beginning of most science courses when the subject of density is introduced. The instructor can make this activity as easy or difficult as he/she chooses. It can be used in biology, chemistry and Earth science classes and can be adapted for use in other settings. Depending on the extent of difficulty, this activity can take from two to three 50 minute class periods.
Description and Teaching Materials
SOILS LABORATORY REPORT
NAME and DATE of activity:
MATERIALS NEEDED: shovel, 1 gal. zip-lock baggie, black magic marker, aluminum foil, 100 mL graduated cylinder, 250 mL beaker, balance, short stem funnel, filter paper, buchner funnel, distilled water, digital pH meter or pH paper.
DENSITY PROCEDURE: 1. Digging approximately 5-6 inches below the surface, obtain about 250 mL samples of each type of prairie soil, transition soil, woods soil, riverbed soil. 2. Place each sample in a 1 gal. zip-lock baggie. 3. Label the bag with the type of soil it contains. 4. In the lab, spread each soil out on aluminum foil and place in a drying oven or hood to dry overnight. 5. Using a graduated cylinder, measure 10 mL of soil. 6. Record its mass in the data table. [It may be helpful to leave the soil in the graduated cylinder and place on the balance remembering each time to subtract the mass of the cylinder.] 7. Measure 20 mL of soil and record its mass. 8. Measure out 30 mL of soil and record its mass repeating this procedure for 40 mL, 50 mL, 60 mL, 70 mL, 80 mL, 90 mL and 100 mL soil samples. 9. Repeat this procedure for each of the four kinds of soil. 10. Plot your mass vs. volume data on a "Scatterplot" using the Excel program with "chart wizard" on a computer. Put in the line.
pH PROCEDURE: 1. Measure 50 mL of soil and place in a beaker. 2. Add 50 mL of distilled water and swirl. 3. Let the soil and water mixture stand for 20 minutes. Measure the soil pH using the pH meter. 3. Repeat this procedure for each of the four kinds of soil.
WATER CONTENT PROCEDURE: 1. Measure 50 mL of soil and place in a beaker. 2. Carefully measure out 100 mL of distilled water in a graduated cylinder. 3. Add about 80 mL of the water to the soil and stir. 4. Pour the soil-water mixture into a buchner funnel-filter paper/erlenmeyer flask apparatus so the "soil" water flows into the flask. 5. Rinse out the beaker with the rest of the water (~20 mL) left in the cylinder. 6. Carefully record the volume of water collected in the erlenmeyer flask.
OBSERVATIONS: Write out at least 5 complete sentences on what you observed during this activity.
DATA: Make a data table(s) for each soil type showing: volume of soil, mass of soil, density of soil, and pH and water content of each soil sample. Make sure you label all data with the correct units. Record the pH of each soil type and the water content of each soil type.
CALCULATIONS: 1. Using your data, detemine the density for each of your measurements of each soil sample. [Show your work for each calculation with correct units!] 2. Show your work on how you calculated a soil type's water content (%).
QUESTIONS: 1. What does the line on your density graphs represent? 2. Compare your densities for each soil sample type. 3. Which soil type had the lowest pH? The highest pH? What does the pH mean? 4. Compare the water contents for each soil sample (%). Which soil type had the highest water content? The lowest water content? What does this suggest? 5. Was there a difference between the amount of water added to the soil and the amount of water measured out afterward? If there was a difference, what did it represent? 6. Did you read the bottom of the meniscus each time you measured something in the graduated cylinder? 7. What safety precautions were necessary in this activity? 8. Compare your results with other student groups and be prepared to discuss your results with the class.
ABOVE and BEYOND: 1. What part of our methodology could have been done differently to make this activity "better?" 2. Besides soil, what other substance(s) could have been used in this activity? 3. Calculate the standard deviation of your soil density data.
ADDITIONAL DENSITY PROBLEMS:
What is the density in g/cm3 of a solid piece of aluminum which has a mass of 95.26 grams and is 4.8 cm long, 3.5 cm wide, and 2.1 cm thick?
Calculate the density of a piece of bone with a mass of 3.8 g and a volume of 2.0 cm3.
A spoonful of sugar with a mass of 0.0088 kilograms is poured into a 10 mL graduated cylinder. The volume reading is 5.5 mL. What is the density of the sugar in g/mL?
A certain brand of butter has a density of 0.872 g/cm3. What volume in liters would 272.0 grams occupy?
Calcium chloride has a density of 2.15 g/cm3 What is the volume in mL of 3.37 grams of this substance?
Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass in grams of the aluminum sample? (Hint: use the density answer in the first problem to help solve)
A piece of metal with a density of 0.007 kg/mL is placed in a 50 mL graduated cylinder. The water level rises from 20 mL to 41 mL. What is the mass in grams of the metal?
You place a 28.95 gram piece of gold in a 10 mL graduated cylinder. The level of water rises 1.50 mL. What is the density of gold? You know that silver has a density of 10.5 g/cm3. What mass of silver will raise the level of the water in the graduated cylinder 1.50 mL?
NAME and DATE of activity:
MATERIALS NEEDED: shovel, 1 gal. zip-lock baggie, black magic marker, aluminum foil, 100 mL graduated cylinder, 250 mL beaker, balance, short stem funnel, filter paper, buchner funnel, distilled water, digital pH meter or pH paper.
DENSITY PROCEDURE: 1. Digging approximately 5-6 inches below the surface, obtain about 250 mL samples of each type of prairie soil, transition soil, woods soil, riverbed soil. 2. Place each sample in a 1 gal. zip-lock baggie. 3. Label the bag with the type of soil it contains. 4. In the lab, spread each soil out on aluminum foil and place in a drying oven or hood to dry overnight. 5. Using a graduated cylinder, measure 10 mL of soil. 6. Record its mass in the data table. [It may be helpful to leave the soil in the graduated cylinder and place on the balance remembering each time to subtract the mass of the cylinder.] 7. Measure 20 mL of soil and record its mass. 8. Measure out 30 mL of soil and record its mass repeating this procedure for 40 mL, 50 mL, 60 mL, 70 mL, 80 mL, 90 mL and 100 mL soil samples. 9. Repeat this procedure for each of the four kinds of soil. 10. Plot your mass vs. volume data on a "Scatterplot" using the Excel program with "chart wizard" on a computer. Put in the line.
pH PROCEDURE: 1. Measure 50 mL of soil and place in a beaker. 2. Add 50 mL of distilled water and swirl. 3. Let the soil and water mixture stand for 20 minutes. Measure the soil pH using the pH meter. 3. Repeat this procedure for each of the four kinds of soil.
WATER CONTENT PROCEDURE: 1. Measure 50 mL of soil and place in a beaker. 2. Carefully measure out 100 mL of distilled water in a graduated cylinder. 3. Add about 80 mL of the water to the soil and stir. 4. Pour the soil-water mixture into a buchner funnel-filter paper/erlenmeyer flask apparatus so the "soil" water flows into the flask. 5. Rinse out the beaker with the rest of the water (~20 mL) left in the cylinder. 6. Carefully record the volume of water collected in the erlenmeyer flask.
OBSERVATIONS: Write out at least 5 complete sentences on what you observed during this activity.
DATA: Make a data table(s) for each soil type showing: volume of soil, mass of soil, density of soil, and pH and water content of each soil sample. Make sure you label all data with the correct units. Record the pH of each soil type and the water content of each soil type.
CALCULATIONS: 1. Using your data, detemine the density for each of your measurements of each soil sample. [Show your work for each calculation with correct units!] 2. Show your work on how you calculated a soil type's water content (%).
QUESTIONS: 1. What does the line on your density graphs represent? 2. Compare your densities for each soil sample type. 3. Which soil type had the lowest pH? The highest pH? What does the pH mean? 4. Compare the water contents for each soil sample (%). Which soil type had the highest water content? The lowest water content? What does this suggest? 5. Was there a difference between the amount of water added to the soil and the amount of water measured out afterward? If there was a difference, what did it represent? 6. Did you read the bottom of the meniscus each time you measured something in the graduated cylinder? 7. What safety precautions were necessary in this activity? 8. Compare your results with other student groups and be prepared to discuss your results with the class.
ABOVE and BEYOND: 1. What part of our methodology could have been done differently to make this activity "better?" 2. Besides soil, what other substance(s) could have been used in this activity? 3. Calculate the standard deviation of your soil density data.
ADDITIONAL DENSITY PROBLEMS:
What is the density in g/cm3 of a solid piece of aluminum which has a mass of 95.26 grams and is 4.8 cm long, 3.5 cm wide, and 2.1 cm thick?
Calculate the density of a piece of bone with a mass of 3.8 g and a volume of 2.0 cm3.
A spoonful of sugar with a mass of 0.0088 kilograms is poured into a 10 mL graduated cylinder. The volume reading is 5.5 mL. What is the density of the sugar in g/mL?
A certain brand of butter has a density of 0.872 g/cm3. What volume in liters would 272.0 grams occupy?
Calcium chloride has a density of 2.15 g/cm3 What is the volume in mL of 3.37 grams of this substance?
Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass in grams of the aluminum sample? (Hint: use the density answer in the first problem to help solve)
A piece of metal with a density of 0.007 kg/mL is placed in a 50 mL graduated cylinder. The water level rises from 20 mL to 41 mL. What is the mass in grams of the metal?
You place a 28.95 gram piece of gold in a 10 mL graduated cylinder. The level of water rises 1.50 mL. What is the density of gold? You know that silver has a density of 10.5 g/cm3. What mass of silver will raise the level of the water in the graduated cylinder 1.50 mL?
Teaching Notes and Tips
A lot of time can be saved (if desired) by having the instructor bring in the already collected soil samples. Different types of soil samples can also be used in this experiement. Students will have questions on how to calculate the soil water content. [e.g. If 100 mL of water was originally used in the soil and 70 mL of water was collected in the erlenmeyer flask, how much water was aborbed by the soil? 30 mL Therefore, the water content of the soil is 30%.] The instructor can decide how much in depth he/she wants to go in discussing the pH of the soils. The activity will reinforce a prior classroom lesson on density, pH and water content. In the past, I used to have students determine the densities of various objects in the classroom. This activity is more interesting for the students and allows for the teaching of pH and water content in the same lesson.
Assessment
Students will be assessed on the Lab Report described above (when it is handed in) as well as similar density questions and problems included in the Chapter Test. The instructor will use a rubric on the Lab Report and will observe students learning and understanding on their various laboratory techniques, collection of data, care of handling lab equipment, safety precautions and laboratory clean up.
Standards
6.II.A.5 - Properties of Matter
8.I.B.3 - Scientific Investigations
8.I.B.3 - Scientific Investigations