The reason for this is because hydrogen peroxide has an extra oxygen atom, While both substances are made of hydrogen and oxygen, water has 2 hydrogen atoms and one oxygen, while hydrogen peroxide has 2 hydrogens and 2 oxygens.
These substances have different properties because H2O2 is negatively charged. It wants to become neutral, and for that to happen it has to be chemically combined with another element to cancel out the -2 charge of the extra oxegyn atom..
If you drank H2O2 you would die because the negative charges of the oxegyn would probably try to take iron from your blood. I think this is the reason why, when you put the H2O2 on a wound it hurts. Because it takes some iron out of your blood. Not sure about that one
