### Instruction: What are the classical states of matter?
### Response: 1. Solid: Matter in a solid state is comprised of particles that are held very closely together. Solids hold a definite shape. 
2. Liquid: Matter is in a mostly non-compressible fluid state. Liquid matter conforms to the shape of its container. 
3. Gas: Matter in a gaseous state is composed of compressible fluids. It may also take the shape of its container, but it will also expand to fill the container.