What is combustion?| Types of substance

The enthalpy combustion of a substance

A substance which reacts with oxygen giving heat is called a combustible substance. Which, one of the following is a combustible substance?

The amount of energy released during complete combustion of 1 gm of substances is its

What are non-combustion substances ?

What are the two types of pure substance ? Give one example of each type.

What are the combustible substances ?