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Settling Rate of Particles of Sediments

based on 3 ratings
Author: Janice VanCleave

So You Want to Do a Project about Settling Rate!

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Purpose

To compare settling rates.

Materials

  • 2-cup (500-mL) measuring cup
  • Tap water
  • 2 1-quart (1-L) plastic jars with lids
  • 1/2 cup (125 mL) flour
  • 1/2 cup (125 mL) dry red beans (pinto beans work well.)
  • Timer
  • Helper

Procedure

Settling

  1. Pour 2 cups (500 mL) of water into each jar.
  2. Add the flour to one jar and the beans to the other jar.
  3. Secure the lid on each jar.
  4. Give your helper one of the jars, and you take the other one. You and your helper should start shaking the jars thoroughly when you say "go" and set them on the table after 30 seconds when you say "stop."
  5. Observe and record the appearance of the contents of each jar in a Settling Rate Data table like the one shown. This will be recorded in the 0 minutes column.
  6. Observe and record the appearance of each jar every 20 minutes for 1 hour. If the flour and beans have not settled after 1 hour, continue to make observations once an hour for 2 or more hours. (You may wish to make your last observation after the jars have stood overnight. Determine the length of this time.)

Results

The beans mixed with the water as long as the jar was being shaken, but settled as soon as the jar was set down. Immediately after shaking, the jar of flour and water appeared cloudy. Most of the flour settled within 20 minutes. The time it takes for all the flour to settle will vary, but for the author's experiment, it took about 3 hours for the water to start looking clear. However, even after sitting all night, there was still some flour floating on the surface of the water, and the water was not totally clear.

Why ?

The shaking of the flour and beans in water represents different size rock particles being transported by fast-moving water. Placing the jars on the table represents the transport of the particles into a stationary (nonmoving) body of water. Rock particles or sediments, like the food particles in this experiment, are carried by swiftly moving bodies of water, such as streams and rivers, then deposited in stationary water, such as a lake. The time it takes a sediment to settle out of its transporting agent is called its settling rate. The settling rate of beans is much faster than that of flour. The flour represents silt (fine-grained sand). Since all the flour did not settle at the same time, this indicates that some flour particles are smaller than others. Larger particles of sediments settle out of water first, followed by progressively smaller particles.

For Further Investigation

In a river, all the particles are mixed together. What kind of layers would be formed if several different size particles were put in the same jar? A project question might be, How does the settling rate of sediment affect horizontal layering in sedimentary rock?

Clues for Your Investigation

  1. Repeat the investigation, using four jars and adding the flour, beans, and water together in each jar.
  2. Photographs of the jars during the investigation can be displayed to represent the changes that occur.
  3. You may wish to replace the flour and beans with soil, sand, and gravel (aquarium gravel can be used).

Settling

References and Project Books

Butterfield, Moira. 1,000 Facts about the Earth. New York: Kingfisher Books, 1992.

Churchill, E. Richard. 365 Simple Science Experiments with Everyday Materials. New York: Black Dog & Leventhal,1997.

Redfern, Martin. The Kingfisher Young People's Book of Planet Earth. New York: Kingfisher Books, 1999.

Rillero, Peter. Science Projects and Activities. Lincolnwood, III: Publications International, 1999.

VanCleave, Janice. Janice VanCleave's Earth Science for Every Kid. New York: Wiley, 1991.

Janice VanCleave's A+ Projects in Earth Science. New York: Wiley, 1999

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