Another pure substance, compounds contain atoms from two or more elements chemically bonded. when atoms bond, they cannot be separated physically. compounds may have different properties than the elements they’re made of. water, for example, is a compound formed from hydrogen and oxygen. water is a liquid at room temperature, while oxygen and hydrogen are both gases. which of the following best describes compounds? a they can only be separated chemically. b they are always liquid at room temperature. c they contain the atoms of just one element. d they have the same properties as their elements.\