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Difficulty: EasySuggesting Experiments to Resolve Viewpoints

Two scientists discuss the conditions necessary for the rusting of iron (FeFe).

Scientist 1
Rusting is a chemical reaction that requires only iron and oxygen (O2O_2) gas. When iron is exposed to O2O_2, it reacts to form iron oxide (rust). Water (H2OH_2O) is not necessary for this reaction to occur.

Scientist 2
Rusting is a chemical reaction that requires only iron and liquid water (H2OH_2O). When iron is exposed to H2OH_2O, it reacts to form rust. Oxygen (O2O_2) gas is not necessary for this reaction to occur.

Which of the following experiments would best determine which scientist's viewpoint is correct?

  1. A
    Placing iron samples in open air at different temperatures and measuring the time it takes for rust to form.
  2. Placing one iron sample in a sealed container with dry O2O_2 gas and another iron sample in a sealed container with deoxygenated liquid H2OH_2O, then observing which sample rusts.Answer
  3. C
    Measuring the rate of oxygen and water consumption as a single iron sample rusts over time in a humid chamber.
  4. D
    Exposing different metals, such as copper and zinc, to a mixture of oxygen and water and comparing their rates of corrosion.

Answer

Placing one iron sample in a sealed container with dry O2O_2 gas and another iron sample in a sealed container with deoxygenated liquid H2OH_2O, then observing which sample rusts.
The correct answer is correct because it isolates the independent variables in question. Scientist 1 claims that oxygen alone is sufficient to cause rusting, while Scientist 2 claims that water alone is sufficient. By placing one iron sample in an environment with only oxygen (dry oxygen gas) and another in an environment with only water (deoxygenated water), the experiment directly tests whether either reactant can produce rust in the absence of the other.

Step-by-Step Solution

1
Identify the core disagreement between the two viewpoints.
Scientist 1 claims that oxygen is required and water is not, whereas Scientist 2 claims that water is required and oxygen is not.
Understanding the conflicting assumptions is necessary to identify which independent variables must be isolated.
2
Determine the required experimental conditions to test these claims.
An experiment must isolate oxygen from water. This requires one setup with iron exposed to only dry oxygen (no water) and another setup with iron exposed to only deoxygenated water (no oxygen).
If rusting occurs in dry oxygen, Scientist 1 is supported. If rusting occurs in deoxygenated water, Scientist 2 is supported.
3
Select the option that matches this isolated design.
The option proposing to place one iron sample in dry oxygen gas and another in deoxygenated liquid water fits this requirement.
This is the only choice that isolates the two independent variables to resolve the specific dispute.

Key Concept

To resolve conflicting scientific viewpoints, an experiment must be designed to isolate and test the proposed independent variables separately while keeping all other conditions constant.
Estimated Time:1m 0s
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Suggesting Experiments to Resolve Viewpoints

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