Question

What happens when ethanol (1) is burnt in air and (2) it is oxidised

Answer 1

When ethanol is burnt in air, carbon dioxide gas is evolved.
C2H5OH + O2 ------> CO2 + H2O

When ethanol is oxidized, we get acetaldehyde or ethanal.

C2H5OH --------> CH3CHO
The oxidizing agent is Acidified Potassium dichromate.