A geologist conducted an experiment to test the following hypothesis: *Hypothesis*: Basalt… — ACT

A geologist conducted an experiment to test the following hypothesis:

*Hypothesis*: Basalt rocks subjected to freeze-thaw cycles will experience a greater percentage loss in mass when saturated with water of lower salinity, because lower salinity water expands more upon freezing, exerting greater pressure within rock pores.

Identical basalt rock samples of the same initial mass were saturated with water of three different salinity levels: $0\text{ g/L}$ (freshwater), $15\text{ g/L}$ (brackish water), and $35\text{ g/L}$ (ocean water). The samples were then subjected to $50$ freeze-thaw cycles between $-10^\circ\text{C}$ and $20^\circ\text{C}$ . The average percentage loss in mass for each group of samples was calculated and recorded in the table below:

Water salinity ( $\text{g/L}$ )	Average mass loss (\%)
$0$	$4.8$
$15$	$3.2$
$35$	$1.5$

Do the results of the experiment support the geologist's hypothesis?

A
Yes, because the average mass loss increased as the salinity of the water increased from $0\text{ g/L}$ to $35\text{ g/L}$ .
Yes, because the average mass loss was greatest for the basalt samples saturated with the lowest salinity water ( $0\text{ g/L}$ ).Answer
C
No, because the average mass loss was lowest for the basalt samples saturated with the lowest salinity water ( $0\text{ g/L}$ ).
D
No, because the average mass loss decreased as the salinity of the water decreased from $35\text{ g/L}$ to $0\text{ g/L}$ .

Answer

The results support the hypothesis because the average mass loss was greatest for the basalt samples saturated with the lowest salinity water (

0\text{ g/L}

The geologist's hypothesis predicts that basalt rocks saturated with water of lower salinity will experience a greater percentage mass loss. According to the table, the basalt samples saturated with water at

0\text{ g/L}

salinity (the lowest salinity tested) had an average mass loss of

4.8\%

, which is the highest mass loss recorded. As salinity increases to

15\text{ g/L}

and then

35\text{ g/L}

, the mass loss decreases to

3.2\%

and

1.5\%

, respectively. This trend demonstrates that lower salinity corresponds to greater mass loss, thereby supporting the geologist's hypothesis.

Step-by-Step Solution

Identify the geologist's hypothesis.

The hypothesis predicts that lower salinity water leads to a greater percentage mass loss in basalt rocks during freeze-thaw cycles.

This establishes the expected relationship between salinity (independent variable) and mass loss (dependent variable).

Analyze the experimental data in the table.

0\text{ g/L}

salinity, mass loss is

4.8\%

. At

15\text{ g/L}

, mass loss is

3.2\%

. At

35\text{ g/L}

, mass loss is

1.5\%

This identifies the actual relationship between water salinity and average mass loss.

Compare the data trend to the hypothesis.

As salinity decreases (from

35\text{ g/L}

0\text{ g/L}

), the average mass loss increases (from

1.5\%

4.8\%

, with the lowest salinity yielding the greatest loss). This matches the hypothesis.

This determines whether the experimental results support or refute the geologist's hypothesis.

Key Concept

Evaluating a hypothesis against experimental data

Estimated Time:1m 15s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic