Answer to Question #2502 in Molecular Physics | Thermodynamics for sana

Question

Why can heat be conducted through solids, liquids and gases but not through vacuum?

Answer 1

Heat(or thermal energy in transit) is the part of the total, internal energy of a thermodynamic system or sample of matter that results in the system's temperature.

Microscopically, the thermal energy is the kinetic energy of a system's constituent particles, which may be atoms, molecules, electrons, or particles in plasmas. It originates from the individually random, or disordered, motion of particles in a large ensemble.

From the above definition we can see that heat micriscopicaly is the energy of particles (atoms,molecules etc.). And vacuum is defined as a volume of space that is essentially empty of matter.The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in practice. So whereas there are no
particles in vacuum , there are no units those could carry heat, so to speak.

Obviously heat can be conducted through solids, liquids and gases, because all the substances mentioned are constructed with particles.