Final answer:
The thermal conductivity of rock salt at 500°C is not provided in the question, but generally, rock salt has low thermal conductivity compared to metals, so it would be moderate or low.
Step-by-step explanation:
The thermal conductivity of a substance is a measure of how well heat is conducted through it. Although the exact thermal conductivity of rock salt at 500°C is not provided in the question, in general, rock salt has relatively low thermal conductivity compared to metals but can be considered moderate when compared to insulating materials. The high temperature of 500°C does not necessarily change its relative conductivity classification, but it should be noted that thermal conductivity can vary with temperature. Even though the specific value at 500°C is not given, we can infer that the thermal conductivity of rock salt at this temperature is likely to remain on the lower end of the scale when compared to other common engineering materials. Rock salt generally has a low thermal conductivity. Thermal conductivity refers to the ability of a material to conduct heat, and in the case of rock salt, it tends to be relatively low compared to some other materials. However, specific values can vary depending on the exact composition and conditions. The provided question does not offer a specific numerical value for the thermal conductivity at 500°C, so we can only provide a general characterization, which is that rock salt typically exhibits low thermal conductivity.