The term "mechanical substance" is not a standard scientific term. There's no established definition or concept in physics, chemistry, or materials science that directly corresponds to "mechanical substance."

Here's why:

* Substances are chemically defined: In chemistry, a substance refers to a pure element or compound with a specific chemical composition. It's not related to mechanical properties.

* Mechanical properties are physical: Mechanical properties describe how a material behaves under stress and strain, like its strength, stiffness, and ductility. They are physical characteristics, not a separate category of substances.

It's possible that "mechanical substance" is used in a specific context or field, but without more information, it's unclear what it might refer to. If you can provide more context, I might be able to offer a more specific answer.

Perhaps you're thinking of:

* Mechanical mixtures: These are mixtures of different materials that can be separated by physical means (e.g., sand and water).

* Mechanical alloys: These are alloys created by mixing different metals, often through mechanical processes like powder metallurgy.

If you have a different understanding of "mechanical substance," please clarify, and I'll do my best to help.