I am going to take a guess. The chemical formula for water is H2O, whereas the chemical formula for hydrogen peroxide is H2O2. Therefore, though they are both composed of hydrogen and oxygen, they differ in their ratios of hydrogen to oxygen. In water, the ratio of hydrogen to oxygen is 2:1. In hydrogen peroxide, the ratio of hydrogen to oxygen is 2:2 (or 1:1). Hence, because of the difference in ratios, these two molecules exhibit unique chemical and physical properties.
