Mud Shake

Objective

In this activity, students determine the composition of a soil sample by separating the soil particles into layers. Students will then classify the soil as sand, silt, or clay.

Making the connection:

Activity

Hypothesize

Is the soil at the field site mostly sand, silt or clay?

Plan it!

  • Use a measuring cup to collect a sample of about 2 cups of soil from your field site. Put the sample into a Ziplock bag and seal it tightly. If you are doing this activity along with the Soil Temperature Test, Texture Test, the Percolation Test, and the Compaction Test, you should collect the soil from the same place. Collecting soil from the same quadrant allows students to put the results of all four tests together to form a more complete picture of the soil at their site.
  • Make sure you have a good place for your sample to sit undisturbed. You will need to be able to check your results on the day following this activity. If not, you should plan the test for another day.
  • Remove the label from your plastic bottle so that you will be able to see the sample clearly.
  • Use a permanent marker to write your name, or the name of your group, near the top of the bottle.

Do it!

  1. Fill a 2-liter bottle with water until it is two-thirds full.
  2. Add soil from the sample you collected to the bottle, using the funnel, until the bottle is almost full.
    Be sure students add the soil slowly so they do not overfill the bottle. It is not necessary for all the soil collected to fit into this bottle.
  3. Tightly seal the bottle with its cap.
    You may want to check that the caps are on tight before students move to the next step.
  4. Shake the bottle for 1-2 minutes, or until it is well mixed.
    This can seem like a long time when students are just shaking the bottle. You can put on music and ask the kids to dance and shake the bottle until the music stops. You may want to do this step outside to avoid possible mess if a cap isn't on tight.
  5. Let the bottle sit untouched for 24 hours.
  6. After 24 hours, observe the layers forming in the bottle. Use the Underground Adventure Field Guide to help identify the different types of soil you see.
    Encourage students to make as many observations as possible. You may want to pause and ask some students or groups to share their observations, then allow some additional time for observation. This will allow student groups to compare what they are seeing.

Record it!

Remember, be sci-wise!

  • Pour the soil into the funnel slowly. It will take some time for the funnel to empty into the bottle.
  • Make sure your bottle has a tight seal so it doesn't leak while you shake it.
  • Make sure the bottle doesn't move for 24 hours to keep the soil and water from remixing.
  • If you need to move the bottle in order to observe it more easily, move it carefully and try not to shake it.

Assessment and Reflections

  • Which kinds of particles did you see in your sample?
    Students may observe up to three layers of soil in their bottle, depending on the soil they test. The thickness of layers will depend on how much of each soil type is in the sample. Sand will settle first because it contains the largest and heaviest particles, so it will be found on the bottom. Clay will take the longest to settle out because it is the smallest, so it will be found on the top. Silt will be found in the middle layer. Students also may notice tiny bits of grass or other organic material floating on the top.
  • Based on the data you gathered here, do you think your hypothesis was correct or incorrect?
    Answers will vary.
  • How did your data compare with those of other students and from other parts of your field site?
    Results will vary according the overall composition of the soil at your field site. If some areas contain more clay than others, for example, students in that area would have very different results from students whose quadrant contains more sandy soil.
  • Which type of particle settled first? Last? Why?
    Sand will settle first, because it is the largest and heaviest. Clay will settle last because it is the smallest.
  • Do the results of this activity match the Texture Test results? Did you expect them to? Why or why not?
    Since both tests are designed to measure soil composition, they should yield similar results. However, you may find significant variation between what the students expected and what the Mud Shake shows, particularly if the soil is a loam with a fairly even distribution of sand, silt, and clay.
  • How might the data be different if you used a different soil sample? Why?
    Different soil samples have different compositions. Some may have more sand or more clay, etc.
  • What other variables might affect your results? How?
    One possible answer is remixing of the test sample during the 24 hours.
  • What would you expect to find if you checked your bottle after a week? A month? A year?
    If the bottles remain undisturbed, you may notice the water getting clearer as the days go by. Some of the clay is so tiny that it may never settle, and the water therefore will never be completely clear.
  • Now that you know more about the composition of your soil, would you expect to find many creatures in the soil or just a few? What types of creatures would you expect to see?
    Answers will vary.
  • Looking at the bigger picture, how might the data you gathered here help you to answer your research question?
    Answers will vary based on the research question students are investigating. The important thing is for students to begin to connect the data they gathered in this activity to data from other activities to address their research question.

Extensions

Students can calculate the percentage of each soil type in the sample by:

  1. Measuring the height of the whole sample.
  2. Measuring the height of each layer.
  3. Dividing the height of each layer by the total height of the sample.
  4. Multiplying by 100 to get a percentage.

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