Question

Among metals, the poorest conductor of heat is:
A. lead
B. tin
C. bismuth
D. mercury

Answer 1

Hint:A good conductor of heat is the substance which readily allows heat to pass through it and whose constituent molecules vibrate regularly on the gain of heat. The value of conductance is very high in a good conductor of heat and does not oppose the flow of heat through itself.

Complete step by step answer:
The thermal conductivity of a material is the measure of its ability to conduct heat through that particular metal from one end to another. Heat transfer occurs at a lower rate in materials of lower thermal conductivity than in materials of higher thermal conductivity. For example, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like plastics. Due to this, materials of high thermal conductivity are widely used in heat sink applications such as a Carnot engine, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is known as the thermal resistivity.
Tin, Bismuth and Mercury have high thermal conductivities whereas lead has a low thermal conductivity because lead does not conduct heat through itself and does not allow a heat passage easily from one side to another. This is the reason why lead rods are used for the purpose of cooling in many reactions.

Thus, the correct option is A. lead.

Note: Lead metal has several useful mechanical properties, including high density, low melting point, ductility, and relative inertness. Many metals are superior to lead in some of these aspects but are generally not common and are more difficult to extract from the parent ores. Lead's toxic behavior has led to its phasing out for some uses.