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Settling_Lab

VIEWS: 5 PAGES: 2

  • pg 1
									                                     Particle Settling Time

Introduction
Materials that are transported during erosion and dropped during deposition are bits and pieces of weathered
rock. These pieces of rock may be of almost any size from ions on up to boulders. You can use your Earth
Science Reference Table to determine the size of any particle. Whatever their size, they are called
sediments. The process of deposition is therefore also called sedimentation.

Size of the particle is one important factor in determining the rate at which particles settle out of water.
Layers of sediment can result from different sized particles settling out of the water. If we measure the time
it takes for particles of the same material but of various sizes to settle through the same depth of water, our
data will show a definite relationship between particle size and settling time.

Materials & Methods
       Plastic Tube With Water                    Stop Watch                       Scoop
       3 Different Sized Sediments Samples        Calculator                       Graph Paper

   1. Time how long it takes for a scoop-tip full of each of the 3 pure sediments to fall through the
      column. Start the stopwatch as the sediment is poured, and stop it when the middle of the sediment
      cloud reaches the bottom.
   2. Create the following data table in your “Observations & Data” section. Conduct three trials for each
      sediment size and record the times in your table. Calculate the average time for each sediment.
          Sediment                                                                         Average
            Size              Trial One           Trial Two          Trial Three            Time
           Pebbles
          10 Mesh
         Coarse Sand
          40 Mesh
          Fine Sand
           60 Mesh

   3. Return any extra sediment to the proper container.
   4. Obtain a small cup full of the mixture, pour all of it into the water column. Record your
      observations regarding what happens to the different sizes as they fall through the water. How are
      the sediments arranged on the bottom? Record observations in the appropriate section. It is not
      necessary to use the stop watch for this part.
   5. Make a graphical representation of your data that illustrates the relationship between particle size
      and settling time.

           Important Note: Pebbles are assigned a mesh size of 10 because that sized particle can
           not fall through a sieve that has 10 wires per inch. Mesh size of 40 means that 40 wires
           per inch are used and coarse sand cannot fall through the sieve. More wires means smaller
           holes in the sieve, therefore, fine sand will be trapped in a mesh size of 60.

  60 Mesh = Small Particles                                                             10 Mesh = Larger Particles
   a.     Put the variable mesh size on the horizontal axis. To have the particle size increase from left to
          right, mesh size must decrease from left to right. Therefore, number this axis from 100 to 0.
    b.    Label the y-axis average settling time.
    c.    Plot your data, draw the line of best fit. Use a dashed line (---------) to continue the graph line
          from 60 mesh to 100 mesh and from 10 mesh to 0 mesh.
6. Use all your resources to answer the following questions in your “Conclusion” section. Make sure
    you use complete sentences.
7. What is meant by the term deposition?
8. If all other factors are equal, what effect does particle size have on settling rate?
9. Clay size particles have a mesh size of 225. How would their settling time compare to sand?
10. According to your graph, how long would it take for a particle of mesh size 35 to settle?
11. Particles of what mesh size would take 7 seconds to settle?
12. According to your reference tables what size range are pebbles?

								
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