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Subject Test Chemistry

Question 10 of 17

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SAT Subject Test

Each of the questions or incomplete statements below is followed by five suggested answers or completions.  Select the one that is best in each case.

A thermometer is placed in a test tube containing a melted pure substance. As slow cooling occurs, the thermometer is read at regular intervals until well after the sample has solidified. Which of the following types of graphs is obtained by plotting temperature versus time for this experiment?

Option (A) presents a graph. The horizontal axis is labeled Time, and the vertical axis is labeled Temperature. This graph contains one line or curve that does not touch the axes. The graph shows a curve starting in the upper left area of the graph. The curve slopes steeply down and to the right, and becomes less steep as it approaches the horizontal axis. The curve then slopes up and to the right, gradually becoming steeper, and ends in the upper right area of the graph.
Option (B) presents a graph. The horizontal axis is labeled Time, and the vertical axis is labeled Temperature. This graph contains one line or curve that does not touch the axes. The graph shows a curve starting in the upper left area of the graph. The curve slopes down steeply and to the right, levels out for about half of the time elapsed, and then slopes down steeply and to the right.
Option (C) presents a graph. The horizontal axis is labeled Time, and the vertical axis is labeled Temperature. This graph contains one line or curve that does not touch the axes. The graph shows a curve starting in the upper left area of the graph. The curve slopes steeply down to the right and gradually becomes less steep as it approaches the horizontal axis on the right side of the graph.
Option (D) presents a graph. The horizontal axis is labeled Time, and the vertical axis is labeled Temperature. This graph contains one line or curve that does not touch the axes. The graph shows a straight horizontal line about halfway up the vertical axis that extends from the left side of the graph to the right side of the graph.
Option (E) presents a graph. The horizontal axis is labeled Time, and the vertical axis is labeled Temperature. This graph contains one line or curve that does not touch the axes. The graph shows a straight line that starts in the upper left area of the graph and slopes down to the lower right area of the graph.
 

Select an Answer

(A)

Correct Answer: 
No

(B)

Correct Answer: 
Yes

(C)

Correct Answer: 
No

(D)

Correct Answer: 
No

(E)

Correct Answer: 
No

This is a question on states of matter. You must convert the description of the physical phenomenon given in the question to graphical form. When a liquid is cooled slowly, its temperature will decrease with time. Thus, the first portion of a graph depicting this phenomenon must show a decrease when temperature is plotted against time. When a pure liquid substance reaches its fusion (melting) point, continued cooling will release heat with time as the substance solidifies. During this period there is no drop in temperature. After the substance has completely solidified, further cooling will cause an additional drop in temperature. The only graph shown that accurately depicts the events described is choice (B), which is the correct answer.

Question Difficulty: 
medium