Extensive properties The properties of the system, whose value for the entire system is equal to the sum of their values for the individual parts of the system, are called extensive properties.
For example, total volume, total mass and total energy of a system are extensive properties.

Intensive properties The properties of the system, whose value for the entire system is not equal to the sum of their values for the individual parts of the system, are called intensive properties.
For example, temperature, pressure and density of a system are intensive properties.

Heat and work are path functions because they depend on how a system changes from initial to final state, hence they are state functions.
Thermal conductivity is mainly a function of the motion of the free electrons therefore property of a material, not a path function.