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Settle Down: Turbidity and Water Quality

3. Outside Explorations

In this activity, you will test one characteristic of water—turbidity—using soil samples that you collect in your schoolyard or local neighborhood. At the end of the activity, you will evaluate your data and discuss the affects of turbidity on the plants and animals that live in the water. Then you will brainstorm ideas for preventing increased turbidity from runoff and soil erosion.

Before going outside, make sure you have the following:

Student Worksheet: Turbidity Data (your teacher will give to each group)

Supplies:

  • Graduated cylinder or measuring cup (300 milliliter capacity)
  • Metric measuring spoon or cup (30 milliliter capacity)
  • Clear glass jar with lid
  • Stopwatches or wrist watch with minute and second hands
  • Stirrer
  • White paper
  • Tap water in a bucket or pitcher
  • Soil sample from your schoolyard or local neighborhood.

Instructions:

  1. Go outside and collect a soil sample from your schoolyard or neighborhood.
  2. Prepare your glass jar or container. Fill a graduated cylinder or measuring cup with 300 ml of water. Use this water to fill your clear container as follows:
    1. Add 100ml of water to your jar. Draw a line on the jar at the waterline and mark this line “Zone A – 100 ml.”
    2. Add another 100 ml of water to your jar. Draw a second line on the jar at the new waterline and mark this line “Zone B – 200 ml.”
    3. Add the last 100 ml of water to your jar. Draw a third line on the jar at the new waterline and mark this line “Zone C – 300 ml.”
  3. Add 30 ml of soil and use your stirrer to mix completely. Put the lid on the jar and shake the jar well.
  4. Set the jar down and do not touch it for 10 minutes.
  5. Follow the instructions on the student worksheet, “Turbidity Data,” to make predictions and then document the clarity of the water. Use the stopwatch and collect data on water clarity at 1 minute, 5 minutes, and 10 minutes. It may be helpful to work in pairs. One person uses the stop watch and calls the time at 1, 5, and 10 minutes. The second person makes the observation at the moment the time is called and documents it.