Two students discuss the factors that influence the rate of carbon dioxide (CO_2) producti… — ACT

Two students discuss the factors that influence the rate of carbon dioxide ( $CO_2$ ) production during yeast fermentation.

Student 1
The fermentation rate depends solely on the type of sugar (glucose versus lactose) metabolized by the yeast. Yeast will ferment glucose much faster than lactose. The temperature of the yeast's environment has no effect on the rate of fermentation.

Student 2
The fermentation rate depends solely on the temperature of the yeast's environment. Higher temperatures increase yeast metabolic activity, leading to a higher fermentation rate. The specific type of sugar provided to the yeast does not affect the rate.

Match each hypothesis or claim on the left with the corresponding experimental outcome on the right that would directly disprove (invalidate) that claim.

Student 1's claim that temperature has no effect on the fermentation rate of glucose.Measuring different rates of fermentation at $20^\circ\text{C}$ versus $37^\circ\text{C}$ when using only glucose.
Student 2's claim that the type of sugar has no effect on the fermentation rate at a constant temperature.Measuring different rates of fermentation for glucose versus lactose at a constant temperature of $37^\circ\text{C}$ .
The hypothesis that both temperature and sugar type affect the fermentation rate.Measuring identical rates of fermentation for both glucose and lactose at both $20^\circ\text{C}$ and $37^\circ\text{C}$ .

Answer

Student 1's claim that temperature has no effect is disproved by measuring different fermentation rates at

20^\circ\text{C}

versus

37^\circ\text{C}

with glucose. Student 2's claim that sugar type has no effect is disproved by measuring different fermentation rates for glucose versus lactose at

37^\circ\text{C}

. The hypothesis that both factors affect the rate is disproved by measuring identical fermentation rates across both temperatures and both sugar types.

To invalidate Student 1's claim that temperature has no effect on fermentation, we must vary the temperature while keeping the sugar type constant; showing different rates under these conditions disproves the claim. To invalidate Student 2's claim that the type of sugar has no effect, we must vary the sugar type while keeping the temperature constant; showing different rates under these conditions disproves the claim. To invalidate the hypothesis that both factors affect the rate, we must show that neither temperature nor sugar type has any effect by observing identical rates under all conditions.

Step-by-Step Solution

Identify the independent variable being tested in each claim.

Student 1's claim specifies temperature has no effect, Student 2's claim specifies sugar type has no effect, and the third hypothesis specifies both temperature and sugar type have an effect.

To disprove a claim about a variable having no effect, we must look for an experiment where changing that specific variable results in a change in the fermentation rate.

Match Student 1's claim with the outcome that varies temperature.

Student 1's claim is matched with the outcome that varies temperature (

20^\circ\text{C}

37^\circ\text{C}

) while keeping sugar constant (glucose), resulting in different rates.

If different rates are observed at different temperatures, temperature must have an effect, disproving the claim that it does not.

Match Student 2's claim with the outcome that varies sugar type.

Student 2's claim is matched with the outcome that varies sugar type (glucose vs lactose) while keeping temperature constant (

37^\circ\text{C}

), resulting in different rates.

If different rates are observed with different sugars, sugar type must have an effect, disproving the claim that it does not.

Match the joint hypothesis with the outcome showing no effect for either variable.

The hypothesis that both factors affect the rate is matched with the outcome showing identical rates across all conditions.

If rates are identical across all sugars and temperatures, then neither factor affects the rate, disproving the joint hypothesis.

Key Concept

Identifying experimental outcomes that resolve or invalidate conflicting scientific viewpoints by isolating variables.

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