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Ch.12 - Solids and Modern Materials
All textbooksBrown 14th EditionCh.12 - Solids and Modern MaterialsProblem 5
Chapter 12, Problem 5

Imagine that you have a metal bar sitting half in the sun and half in the dark. On a sunny day, the part of the metal that has been sitting in the sun feels hot. If you touch the part of the metal bar that has been sitting in the dark, will it feel hot or cold? Justify your answer in terms of thermal conductivity.

Verified step by step guidance
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Understand the concept of thermal conductivity: Thermal conductivity is a property of a material that indicates its ability to conduct heat. Metals typically have high thermal conductivity, meaning they can transfer heat efficiently from one part to another.
Consider the scenario: The metal bar is exposed to sunlight on one side, causing that part to absorb heat and increase in temperature. The other part of the bar is in the dark, initially cooler than the sunlit part.
Apply the concept of thermal conductivity: Due to the metal's high thermal conductivity, heat from the sunlit part will be conducted through the metal to the part in the dark. This means the temperature of the dark part will increase over time.
Predict the sensation upon touching: When you touch the part of the metal bar that has been sitting in the dark, it will likely feel warmer than the ambient temperature because heat has been conducted from the sunlit part.
Justify the prediction: The sensation of warmth is due to the efficient transfer of heat through the metal, demonstrating the principle of thermal conductivity. This property allows the metal to distribute heat evenly across its length, even if only part of it is directly exposed to a heat source.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Thermal Conductivity

Thermal conductivity is a material's ability to conduct heat. Metals typically have high thermal conductivity, meaning they can transfer heat quickly from one part to another. In the context of the metal bar, the part exposed to sunlight absorbs heat and becomes hot, while the part in the dark remains cooler due to less heat absorption.
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Heat Transfer

Heat transfer occurs through conduction, convection, or radiation. In this scenario, conduction is the primary mode, where heat moves from the hot part of the metal bar to the cooler part. When you touch the cooler part, it will feel cold because it has not absorbed heat from the environment, and the heat from your hand will flow into the metal, making it feel cooler.
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Heat Capacity

Temperature Gradient

A temperature gradient exists when there is a difference in temperature between two areas. In the case of the metal bar, the sunny side has a higher temperature than the dark side. This gradient drives the flow of heat from the hot side to the cold side, influencing how we perceive temperature when touching different parts of the bar.
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Related Practice
Textbook Question

Two solids are shown below. One is a semiconductor and one is an insulator. Which one is which? Explain your reasoning.

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Textbook Question

For each of the two-dimensional structures shown here (a) draw the unit cell (i)


(ii)

Textbook Question

Shown here are sketches of two processes. Which of the processes refers to the ductility of metals and which refers to malleability of metals? (a)


(b)

Textbook Question

(b) What is the coordination number of each cannonball in the interior of the stack?

Textbook Question

Which arrangement of cations (yellow) and anions (blue) in a lattice is the more stable? Explain your reasoning. (a)


(b)

Textbook Question

Which of these molecular fragments would you expect to be more likely to give rise to electrical conductivity? Explain your reasoning. (a)

(b)