Some elements, like helium, are gases. Each element has its own special properties. When you combine the elements iron and oxygen you get a compound called rust. A compound may form when two or more elements are put together. The compound salt is made up of the elements sodium and chlorine.
Water is a compound, too.
It is made of the elements hydrogen and oxygen. Remember that when a mixture is formed, different types of matter are combined together. The properties of the matter in the mixture are not changed. However, the properties of a compound are different from the properties of the elements that make it up.