Final answer:
Compounds are formed by combining two or more elements and have different properties from their component elements. This can be seen in the formation of water, where two hydrogens and one oxygen combine to form a water molecule.
Step-by-step explanation:
A compound is any combination of two or more different elements. A compound has different properties from the elements that it contains. Elements and combinations of elements (compounds) make up all the many types of matter in the Universe. A chemical reaction is a process that breaks or forms the bonds between atoms of molecules and compounds. For example, two hydrogens and one oxygen combine to form a water molecule, which is a compound.