Question

Which of the following is the very poor conductor of heat?

A. Water
B. Metals
C. Liquid other than water
D. Steam

Answer 1

Hint: Lesser is the packing density of a substance, lesser is the ability to transfer heat. You know, vibrational energy leads to the transfer of heat.


Complete step-by-step answer:
Heat energy is the product of the movement of tiny particles in solids, liquids and gases called atoms, molecules or ions. It can transfer heat energy from one object to another. The transition or flow is called heat because of the difference in temperature between the two objects. Evidently, heat energy is all around us: in volcanoes, icebergs, and our body. All matter absorbs energy from the sun.

Particles have greater energy at higher temperatures. Some of this energy can be transferred to other lower-temperature particles. For example, when a fast-moving particle collides with a slower moving particle in the gas state, it transfers some of its energy to the slower moving particle, increasing the particle 's velocity.

All the heat energy, including fire generated heat, is transferred in various ways:
->Convection is a type which transfers energy from heat through liquids and gases.
->Conduction is a type which transfers energy from heat through solids.
->Radiation is a type of transfer that does not require any particles to carry the energy. In fact, it behaves more like electromagnetic waves.

Water is among all poor conductors. Since it is liquid and liquids normally have lower conductivity to heat than solids. The closer the molecules are kept, the more the vibrational energy will pass between them; the heat is nothing more than molecules that vibrate. Since, the molecules in metals are very closely packed, hence the energy of heat is transmitted fully, without losses. Metals are good conductors of heat. However, steam is also a good conductor of heat, as steam is preferred to convert heat to electric power because each gram of steam can provide \[2260{\text{ J}}\] of heat.

Hence, the correct option is (A).

Note: In this question you are asked to find the poor conductor of heat. It is obvious that if the molecules are tightly packed, then vibration energy can be transmitted from a hotter region to a cooler region without any significant loss. Note that the vibrational energy is nothing but heat.