Final answer:
The correct classification for a substance that weakly conducts electricity and does not react with metals is a semiconductor. Semiconductors like silicon are used in electronics and have properties between those of conductors and insulators.
Step-by-step explanation:
A substance that does not react with metals and only weakly lights a conductivity tester is a semiconductor. Semiconductors are materials that conduct electricity better than insulators but not as well as conductors, such as silicon. This characteristic is due to the number of free charges in the semiconductor, which can be influenced by the presence of impurities.
On the other hand, conductors have a large number of free charges that allow for easy movement of electricity. In contrast, insulators have their electrons and ions bound within the structure, making it difficult for electricity to flow through them.
Therefore, given the student's description, the most fitting answer is a semiconductor, which aligns with the characteristic of weak conductivity and inertness towards metals.