Final answer:
Oxidising substances are those that accept electrons during a chemical reaction, a process known as oxidation. The correct answer to the student's question is that oxidising substances are ones that lose electrons.
Step-by-step explanation:
Oxidising substances are those that accept electrons in a chemical reaction. This process is referred to as oxidation, which historically was associated with a substance reacting with oxygen to form oxides. In modern chemistry, however, oxidation has a broader meaning; it refers to the loss of electrons by a substance, which causes an increase in its oxidation state. The term 'oxidizing agent' is used to describe a substance that induces oxidation by accepting electrons and thus gets reduced itself. This concept is part of the broader category of redox reactions, where oxidation and reduction processes happen concurrently.
Based on the definitions provided, the correct identification for oxidising substances is option 2) Substances that lose electrons in a chemical reaction, because the substance that loses electrons is said to be the oxidizing agent, while the one that gains electrons is being reduced.