It depends on how specific and scientific you want to be. I think most people would answer this in a similar way. Example: "oh, that ring is made of gold!" Even though it might not be PURE gold. 1) is asking exactly what (of the many possibilities) substance it is made of. So an answer might be: it is made of gold. 2) is asking what *type* or *category* of substance it is made of. An example answer might be: it is a pure substance such as gold. Or it is a compound substance such as a compound metal (more than 1 type). If you are talking with a chemist, electrician, construction worker, jeweler, etc, the questions are different. If it's just casual conversation, they'll be treated the same generally.

The difference between these two questions is that the first one is asking what specific substance an item is made of, while the second one is asking what kind of substance (e.g. metal, plastic, etc.) it is made of.

Hi Ootred, These are both fine and mean the same thing.

I agree with Jessica, not Daisy. They don't mean the same thing. Q: What substance? A: Steel, rubber, titanium, plastic, carbon fiber, etc. Q: What type of substance? A; A hard metallic material, a flexible material, a heat-resistant substance, etc.