Select all the ways in which two substances can be different. Two substances can be composed of different chemical elements. Two substances can be composed of molecules that contain the same chemical elements but have different numbers of atoms of each element. Two substances can be composed of the same chemical elements, but the substances can have crystal structures with atoms that are arranged differently. Submit

1. **Different Chemical Elements** Two substances made up of different chemical elements are inherently different. For example, one substance might be composed of \( \text{Na} \) and \( \text{Cl} \) (sodium chloride) while another might contain \( \text{K} \) and \( \text{Br} \) (potassium bromide). 2. **Different Numbers of Atoms in Molecules (Different Molecular Formulas)** Even if the molecules of two substances are built from the same set of chemical elements, they can differ if they have different numbers of atoms of each element. This difference in molecular formula means the substances are different. For instance, water (\( \text{H}_2\text{O} \)) and hydrogen peroxide (\( \text{H}_2\text{O}_2 \)) are both composed of hydrogen and oxygen but have different ratios of these atoms. 3. **Different Arrangements or Crystal Structures** Substances can also differ in the way atoms are arranged, even if they are composed of the same chemical elements in the same proportions. A classic example is carbon, which can exist as graphite or diamond. Both are pure carbon (\( \text{C} \)) but have different crystal structures resulting in distinct physical properties. Each of these ways illustrates a valid difference between substances.