Question 40 Answer and Explanation _ACT December 2014 Asia Form 65B Science Section

Passage VII

Introduction

Two solid metal cylinders (X and Y) have the same length and cross-sectional area. Cylinder X is made of hypothetical Metal X, and Cylinder Y is made of hypothetical Metal Y.

Both cylinders are at 25°C. The exterior of each cylinder is insulated everywhere except at one end. Two students are asked the following question: If the 2 cylinders are dropped into a container of boiling water at the same time, the insulated end of which cylinder will reach 50°C first?

Relevant physical properties for Cylinder X and Metal X are listed in Tables 1 and 2, respectively. The value of each physical property for Cylinder X (Metal X) is expressed as a multiple of the value of the same physical property for Cylinder Y (Metal Y).

Each student proposed a different answer to the question they were asked.

Student 1

Because TC of Metal X is 2 times that of Metal Y and the cylinders are the same size, the rate of heat conduction within Cylinder X will be 2 times that within Cylinder Y. Therefore, the rate at which heat flows into Cylinder X will be 2 times the rate at which heat flows into Cylinder Y, and the insulated end of Cylinder X will take half as long as the insulated end of Cylinder Y to reach 50°C.

Student 2

The heat capacity (HC) of each cylinder equals SH of the metal times the mass of the cylinder, so HC of Cylinder X is 4 times HC of Cylinder Y. Thus, to reach 50℃, the insulated end of Cylinder X must absorb 4 times as much heat as the insulated end of Cylinder Y. Because the rate at which heat flows into Cylinder X will be only 2 times that for Cylinder Y, the insulated end of Cylinder X will take 2 times as long to reach 50°C as the insulated end of Cylinder Y.

40. Student 1 would hypothesize that if the 2 cylinders were brought to 50°C and then were dropped into ice water, the insulated end of Cylinder X would take half as long as that of Cylinder Y to reach 0°C. Student 1's hypothesis is most likely based on the assumption that:

F. TC for each cylinder is less when the cylinder is cooled than when the cylinder is heated.

G. TC for each cylinder is the same when the cylinder is cooled as when the cylinder is heated.

H. SH for each cylinder is less when the cylinder is cooled than when the cylinder is heated.

J. SH for each cylinder is greater when the cylinder is cooled than when the cylinder is heated.

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

Student 1 has been discussing the influence of TC on the rate of temperature change, so options H and J are excluded;

Because the TC of a material remains unchanged is an objective fact, so choose G< /p>