You are given a substance. How would you experimentally determine if it is a solid, liquid, or gas at room temperature? List at least three observations you would make.

To determine if a substance is a solid, liquid, or gas at room temperature, I would make the following observations: 

1. Shape and Volume: Observe if it has a definite shape and a definite volume (solid), a definite volume but takes the shape of the container (liquid), or neither a definite shape nor volume (gas). 
2. Compressibility: Try to compress it. If it's highly compressible, it's likely a gas. If it's almost incompressible, it's a solid or liquid. 
3. Flow/Rigidity: Observe if it flows easily (liquid/gas) or is rigid and does not flow (solid). For example, try to pour it. Solids won't pour, liquids will, and gases will disperse.