How does natural selection produce adaptations in a species?

Well the organism that is producing an offspring is already very adapted to it's surroundings. So, the organism has developed characteristics that help it survive in it's environment. These traits are passed down to the offspring. Creating adaptations to this particular species.

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

It will appear as o2(g) as a reactant