In heat transfer and everyday materials science, which one of the following is a poor (bad) thermal conductor compared with the others?

Introduction / Context:
Thermal conductivity is a measure of how easily heat flows through a material. Good thermal conductors quickly transfer heat, while bad (poor) conductors act as insulators and slow down heat flow. Understanding which common materials conduct heat well helps explain why certain metals are used for cooking utensils and why some materials are used for insulation or window panes. This question asks you to identify which listed material is a poor conductor of heat.

Given Data / Assumptions:

• Aluminium, copper, and silver are all metals.
• Glass is a non metallic, brittle solid used in windows and containers.
• Metals are generally good conductors of heat and electricity.
• Non metals like glass are usually much poorer conductors of heat.

Concept / Approach:
Metals conduct heat efficiently due to the presence of free electrons that can move through the lattice and transfer energy. Among metals, silver and copper are especially known for their excellent thermal and electrical conductivity; aluminium is also a good conductor, commonly used in cookware and heat sinks. Glass, however, lacks free electrons and relies on lattice vibrations (phonons) for heat transfer, making it a relatively poor conductor. As a result, glass and similar materials are often used where moderate insulation is acceptable, such as in windows or laboratory apparatus that should not heat up too quickly.

Step-by-Step Solution:
Step 1: Identify the metals in the list. Aluminium, copper, and silver are all metallic elements and known good conductors of heat. Step 2: Recall their common uses. Copper and silver are used in electrical wiring and high quality cookware due to their excellent conductivity. Aluminium is used in pans, pots, and heat sinks because it transfers heat efficiently. Step 3: Examine glass. Glass is an amorphous or partially crystalline non metal; it does not conduct heat as well as metals and is considered a poor thermal conductor. Step 4: Conclude that glass is the bad conductor in the given list.

Verification / Alternative check:
Practical experience supports this classification. A metal spoon placed in hot tea becomes hot quickly along its length, showing good thermal conductivity. A glass handle or a glass tumbler heats much more slowly and is often comfortable to hold even when containing a warm drink, indicating poorer heat transfer. Engineering data also show that thermal conductivity values for metals like silver, copper, and aluminium are orders of magnitude higher than those for glass. This confirms that glass is a bad conductor of heat relative to the listed metals.

Why Other Options Are Wrong:
Option A (Aluminium): Aluminium is widely used where good heat conduction is needed, such as in cookware and radiators. Option B (Copper): Copper is one of the best thermal conductors and is commonly used in high performance heat transfer applications. Option D (Silver): Silver is one of the best conductors of heat and electricity known and cannot be classified as a poor thermal conductor.

Common Pitfalls:
Students may confuse thermal and electrical conductivity or think that any brittle solid like glass must be a good conductor because it is hard. Another confusion comes from the fact that glass can feel cold to the touch, which is more about surface temperature than conductivity. Remember that metals with free electrons are generally excellent conductors, while non metallic solids like glass, wood, and plastics are typically insulators or poor conductors of heat. This distinction is fundamental in both physics and everyday technology.

Final Answer:
Among the given materials, the bad thermal conductor is Glass.