How do you heat gas, minerals to determine what it is made of?

You make them to glow.

Tipically you first make them gases. Solids have continuous spectrum. Gases have discrete lines of emission and absorption. These lines are kind of the ID of different elements and chemicals.

44 minutes ago, Brainee said:

How do you heat gas, minerals to determine what it is made of?

What do you mean gas, minerals ?

You can put solids or liquids into an 'ignition tube' and heat in a bunsen burner flame.
Or you can put some on a carbon block or in a crucible and heat with a blowpipe.

As others have said to heat gas you normally pass an electric discharge through to make it glow.

Using an ignition tube is a chemical test or tests. Does it give off a gas?, does it burn? does it decompose totally? If so what colour changes are there and so on.

Glow discharge methods require some sort of spectroscopic analysis of the light of the glow (which may only be visual).

Adding to what @studiot said, you can study the molecular structure of something by turning it into a crystal, and study the diffraction pattern. That's not exactly heating it. It's how Rosalind Franklin obtained the spatial patterns of DNA that helped Watson and Crick understand its structure. 

I hope we're converging to a satisfactory explanation here, but some feedback would be nice.

I hope that helps.