Which one of the following pairs of metals are very good conductors of heat?

Concept: 

• Thermal conductivity is nothing but the measure of the ability of the material to transfer heat when its temperature is raised.
• It is an intrinsic property.
• Metals which are having higher value of thermal conductivity & are referred to as good conductor of heat.
• The S.I unit of thermal conductivity is Wm-1K-1 

Explanation: 

• Thermal conductivity of any material is decided by two factors.
  • Motion of free electrons
  • Lattice vibrations
• In case of solids, since atoms or molecules are tightly packed & it is more difficult for the electrons to flow even at higher temperature & hence it's thermal conductivity decreases with temperature.
• Given below is the data table for thermal conductivity.
• Clearly we can see that silver & copper have greater value of thermal conductivity as compared to remaining elements.
• Hence both these metals silver & copper are the good conductor of heat.

Additional Information

• Transfer of heat is dependent upon the movement of molecules that results in increase in molecular velocity & hence thermal conductivity.
• Thermal conductivity of gases increases with increasing temperature but for liquids, it decreases with temperature because of expansion & increasing separation between the molecules.
• If we increase the temperature, there is change in the electronic properties of metals due to which number of free electrons & hence lattice vibration increases.