Which of the following statements is not true regarding conduction of heat?

Concept: Conduction is the transfer of heat through direct contact between particles, driven by molecular collisions that pass kinetic energy from hotter to cooler regions without any bulk movement of matter. This mechanism operates in solids, liquids, and gases alike — conduction is fastest in solids (particles are tightly packed and vibrate against neighbours), slower in liquids, and slowest in gases (particles are widely spaced and collide less frequently), but it is never absent in any of the three states.

Application: The question asks for the statement that is NOT true. Checking the claim that conduction does not take place in gases against the concept above: gas molecules do collide with each other and with surrounding surfaces, so conduction does occur in gases — only at a much slower rate than in solids or liquids, since convection tends to dominate heat transfer in gases and fluids. Because this claim denies conduction in gases altogether, it contradicts the physics and is the false statement being asked for.

Cross-check: Testing the remaining three statements against the same concept confirms each of them holds:

• The claim that solids conduct heat faster than liquids matches the concept — closely packed particles in a solid transfer vibrational energy more efficiently than the more loosely arranged particles of a liquid.

• The claim that two objects must be in contact for heat to flow between them matches the defining feature of conduction, which requires direct particle-to-particle contact (unlike radiation, which needs no medium at all).

• The claim that all materials do not let heat flow through them in the same way matches the concept — different materials have different thermal conductivities, which is exactly why conductors (like metals) and insulators (like wood or rubber) behave so differently.

Since the other three statements are consistent with how conduction actually works and only the gases claim denies a real physical process, the statement that conduction does not take place in gases is the one that is not true.