This is the 2168th most frequent Russian word.
вещества
Substances.
In this context, "вещества" is used to refer to chemical substances or materials.
Химические вещества обладают разнообразными свойствами.
Chemical substances have diverse properties.
Here, "вещества" refers to substances in a biological or nutritional context.
В организме человека есть множество полезных веществ.
The human body contains a variety of useful substances.
In this usage, "вещества" pertains to general substances being studied in a scientific setting.