Final answer:
Heat travels fastest in solids because their tightly packed atoms enable efficient transfer of vibrations. In contrast, the wide separation of gas atoms leads to less frequent collisions and slower heat transfer. Conductive materials are typically good heat conductors due to more frequent atomic collisions.
Step-by-step explanation:
The reason heat travels fastest in solids and slowest in gases comes down to the arrangement of atoms and molecules and their interactions. In solids, atoms are tightly packed and interconnected, enabling heat to transfer quickly via vibrations through the solid structure. In contrast, the atoms and molecules in gases are much more spread out, resulting in less frequent collisions and consequently slower heat transfer. Additionally, good conductive materials like metals are excellent at transferring heat due to high-density atoms that collide and transfer energy more effectively.