Regarding chemical precursors, I will go exactly by the definition given in the Controlled Drugs and Substances Act. Precursors are the substances listed in schedule 6 of the act. The definition of “chemical precursor” refers to that schedule.
The term is used not only in Canada but internationally to include substances that will or can be used frequently in the illegal production of controlled substances. So it is used not only in the case of methamphetamine. Other controlled drugs or synthetic drugs can be used or produced with the chemical precursors. The terms “precursors” and “chemicals” can be used interchangeably because people often alternate between using one or the other or combining them.
As for the word “substances”, it depends once again on the context. A definition in the Controlled Drugs and Substances Act talks about controlled substances. There is a reference to another definition, which includes all substances indicated in schedules 1 to 5 of the Act. The schedules list the drugs and pharmaceutical products that are often found on the market. Morphine and methamphetamine are examples that often come up in a legal context.