Download 24. Weathering Rates

Name ___________________________________
Date _______________
Class Period _____
Instructor _____________
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5 points
Weathering Rates
Draw the reaction in the beakers below. Label your drawing.
60 points
QUESTIONS:
1.
3 POINTS EACH
Use complete sentences for questions #1-3.
2.
3.
4.
5.
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Particle Size
Particle Size
7.
6.
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Surface Area
8.
A
B
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9.
A
B
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10.
A
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11.
A
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Surface Area
Lab # 24 Weathering Rates
INTRODUCTION:
Weathering is the gradual breaking up of rocks into smaller and smaller particles, due to the
interaction of the rocks with the atmosphere (air) and hydrosphere (water). Scientists have
found that rocks weather at different rates under different conditions, and that particle size is
a factor that affects the rate of weathering. Given equal volumes of rock, smaller particles
have a greater surface area, which increases the rate of the chemical reaction.
PROCEDURE:
PHYSICAL WEATHERING: Place one ALKA-SELTZER tablet into a piece of notebook
paper folded in half twice (quartered). Using a pestal, smash the tablet (physical weathering)
until it is a powder.
CHEMICAL WEATHERING: Fill two identical beakers with equal amounts of water. At
the same time, place the crushed tablet into one beaker and the whole tablet into the other
beaker. Watch the reactions in both beakers, comparing strength and time of reaction.
QUESTIONS:
1.
What difference in reaction rates was observed.
2.
State the relationship between particle size and reaction rates.
3.
State the relationship between surface area and reaction rates.
4. – 7 Draw the general trends for the graphs on the answer sheet.
8.
If a rock is ground into a powder, the rate at which the powder would chemically
weather, compared to the original rock, would be
A)
B)
C)
D)
slower because the surface area would be less
slower because the surface area would be greater
faster because the surface area would be less
faster because the surface area would be greater
9.
How do chemical and physical weathering differ?
A)
B)
C)
D)
chemical weathering changes the size of the rocks whereas physical weathering
does not
physical weathering changes the size of the rocks whereas chemical weathering
does not
chemical weathering changes the composition of the rocks whereas physical
weathering does not
physical weathering changes the composition of the rocks whereas chemical
weathering does not
Base the answers to questions #11 and 12 on the diagram below which represents
equal masses of two identical rock samples. Sample A is one large block, while
sample B was cut into four smaller blocks of equal size.
Sample A
10.
If subjected to the same environmental conditions, sample B will weather more quickly
than sample A. The best explanation for this is that the
A)
B)
C)
D)
11.
Sample B
surface area of sample B is greater than that of sample A
volume of sample B is greater than that of sample A
density of sample A is greater than that of sample B
hardness of sample A is greater than that of sample B
Compared to sample B, sample A will weather:
A)
B)
C)
D)
slower because the surface area would be less
slower because the surface area would be greater
faster because the surface area would be less
faster because the surface area would be greater