A student hypothesized that as the concentration of salt (\text{NaCl}) dissolved in water … — ACT

A student hypothesized that as the concentration of salt ( $\text{NaCl}$ ) dissolved in water increases, the boiling point of the water decreases. To test this, the student added different masses of $\text{NaCl}$ to $100\text{ mL}$ of pure water and recorded the boiling point of each solution. The results are shown in the table below:

Trial	Mass of $\text{NaCl}$ added ( $\text{g}$ )	Boiling point ( $^\circ\text{C}$ )
1	0	100.0
2	5	100.5
3	10	101.0
4	15	101.5

Based on these results, how should the student modify their hypothesis?

A
Modify the hypothesis to state that the boiling point of the water remains constant regardless of the concentration of $\text{NaCl}$ .
Modify the hypothesis to state that as the concentration of $\text{NaCl}$ increases, the boiling point of the water increases.Answer
C
Modify the hypothesis to state that as the concentration of $\text{NaCl}$ increases, the boiling point of the water decreases.
D
Modify the hypothesis to state that as the concentration of $\text{NaCl}$ increases, the boiling point of the water decreases by $0.5^\circ\text{C}$ for every $5\text{ g}$ of $\text{NaCl}$ added.

Answer

Modify the hypothesis to state that as the concentration of

\text{NaCl}

increases, the boiling point of the water increases.

The experimental data show that as the mass of dissolved salt increases, the boiling point of the water increases from

100.0^\circ\text{C}

101.5^\circ\text{C}

. This contradicts the student's initial hypothesis that the boiling point would decrease. Therefore, the hypothesis must be modified to state that the boiling point increases as the salt concentration increases.

Step-by-Step Solution

Analyze the student's initial hypothesis.

The student proposed that increasing salt concentration decreases the boiling point of water.

Understanding the starting hypothesis is necessary to determine how it should be modified.

Examine the experimental data in the table.

As the mass of salt increases from

0\text{ g}

15\text{ g}

, the boiling point increases from

100.0^\circ\text{C}

101.5^\circ\text{C}

Analyzing the empirical data reveals the actual relationship between the variables.

Compare the observed data trend with the initial hypothesis and modify it accordingly.

The data shows that the boiling point increases rather than decreases. The hypothesis must be modified to reflect this direct relationship.

A scientific hypothesis must be revised when experimental evidence contradicts its initial prediction.

Key Concept

Formulating and Modifying Hypotheses

Estimated Time:45s

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