Students conducted two studies to investigate heat conduction in metal rods. In both studi… — ACT

Students conducted two studies to investigate heat conduction in metal rods. In both studies, a wax bead was placed at one end of a metal rod, and the other end was heated using a Bunsen burner. The time required for the wax bead to melt was recorded.

Study 1
Rods of copper, aluminum, and iron, all with a length of $15\text{ cm}$ and a diameter of $0.5\text{ cm}$ , were tested. The flame height of the burner was kept constant at $3\text{ cm}$ .

Study 2
Copper rods with a diameter of $0.5\text{ cm}$ and lengths of $10\text{ cm}$ , $20\text{ cm}$ , and $30\text{ cm}$ were tested. The flame height of the burner was kept constant at $3\text{ cm}$ .

Which of the following statements best describes a difference between the experimental designs of Study 1 and Study 2?

Study 1 varied the material of the rods while keeping their length constant, whereas Study 2 varied the length of the rods while keeping their material constant.Answer
B
Study 1 varied the length of the rods while keeping their material constant, whereas Study 2 varied the material of the rods while keeping their length constant.
C
Study 1 varied the diameter of the rods while keeping the burner flame height constant, whereas Study 2 varied the burner flame height while keeping the rod diameter constant.
D
Study 1 varied the burner flame height while keeping the rod material constant, whereas Study 2 varied the rod material while keeping the burner flame height constant.

Answer

Study 1 varied the material of the rods while keeping their length constant, whereas Study 2 varied the length of the rods while keeping their material constant.

In Study 1, the type of metal (copper, aluminum, iron) was varied while keeping the length of the rods constant at

15\text{ cm}

. In Study 2, the length of the copper rods was varied (

10\text{ cm}

20\text{ cm}

30\text{ cm}

) while keeping the material constant (copper). Thus, the correct answer correctly identifies that Study 1 varied the material with constant length, whereas Study 2 varied the length with constant material.

Step-by-Step Solution

Identify the independent variable (what is changed) in Study 1.

The rod material (copper, aluminum, iron) is varied, while rod length (

15\text{ cm}

), diameter (

0.5\text{ cm}

), and flame height (

3\text{ cm}

) are kept constant.

Understanding the design of Study 1 requires identifying which parameters are systematically changed and which are controlled.

Identify the independent variable (what is changed) in Study 2.

The rod length (

10\text{ cm}

20\text{ cm}

30\text{ cm}

) is varied, while rod material (copper), diameter (

0.5\text{ cm}

), and flame height (

3\text{ cm}

) are kept constant.

Understanding the design of Study 2 requires identifying which parameters are systematically changed and which are controlled.

Compare the independent and constant variables between the two designs to find the differences.

Study 1 changes the material while keeping length constant; Study 2 changes the length while keeping material constant.

Comparing the designs reveals how they target different variables to isolate their respective effects on heat conduction time.

Key Concept

Comparing and Contrasting Multiple Experimental Designs

Estimated Time:1m 30s

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