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Classroom activity:
Exploring the Sands
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Purpose:
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Students will compare two samples collected from the same beach to explore
the reasons for differences in grain size.
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Materials:
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Two sand samples collected from a San Francisco Beach. One labeled
"F" for fore beach and the other labeled "B" for back beach.
Graduated cylinder
Hand lens
Sieve set. Two sieves should be used, each with a different mesh
size, so that the sand can be separated by grain size into coarse,
medium, and fine.
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1. Observations:
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Using the hand lens, observe each sand sample and record observations
for each sample on the back of this paper.
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2. Predict:
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Predict what you expect to see when you compare the grain size of the
sand collected from the back beach to that collected from the front beach.
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3. Measure, sieve and record:
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Using the graduated cylinder, measure the total volume of sand for
one sample. Record below.
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Pour the sample into the sieve set and shake over a piece of paper
to separate the sand by grain size: coarse, medium, and fine.
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Pour the amount of fine sand that passes through the sieves and is
collected in the paper into the graduated cylinder. Measure and record
below.
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Pour the coarse sand trapped in the first sieve onto the paper and
pour into the graduated cylinder. Measure and record below.
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Subtract from the total and determine the volume of medium-grained
sand. Record.
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Repeat with the second sand sample
Total volume of Sample F:________
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Total volume of Sample B: _______
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Volume of fine-grains:___________
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Volume of fine-grains: __________
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Volume of medium-grains:________
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Volume of medium-grains: _______
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Volume of coarse-grains: _________
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Volume of coarse-grains: ________
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4. Interpret:
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Discuss the differences between the two samples. What do you think is
responsible for these differences?
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5. Results from teacher teams:
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Hypotheses were made, tested, and in some cases revised
as shown below:
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Results from sieving the beach sand: F = Forebeach B = Backbeach
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Amount of
Fine Sand
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Amount of
Medium Sand
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Amount of
Coarse Sand
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Group #1
F
B
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5 ml
0.5 ml
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5.5 ml
29 ml
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1 ml
4.5 ml
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Group #2
F
B
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14 ml
4 ml
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10 ml
8 ml
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6 ml
20 ml
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Group #3
F
B
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2 ml
0.3 ml
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29 ml
25 ml
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2 ml
9 ml
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Group #4
F
B
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>5%
30%
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40%
50%
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50%
20%
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Discussion:
The slope of the back beach is less.
The sand's origin is terrestrial from cliff erosion. It is coarser
near the source of origin.
Energy transfer - waves carry finer materials further. Heavier grains
stay closer to source of origin.
Wave action removes finer materials.
There is an "energy of removal" and an "energy of accumulation".
Wind is another distributing factor of sand.
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Click here for a text-only, student version
of this activity.
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