how are pure carbon, oxygen, hydrogen different from thecompoundethanol which contains all three of those elements

Carbon, oxygen, & hydrogen may all be elements found in ethanol, but when separated, they have completely different chemical compounds. They are pure elements where as ethanol is a mixture.

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.