Final answer:
The statement is true; if a substance contains more than one element, it is not necessarily a mixture as it could be a compound, which is a pure substance with a constant composition. Elements and compounds are pure substances while mixtures are physical combinations of two or more pure substances, which can be homogeneous or heterogeneous.
Step-by-step explanation:
The statement that even if a substance contains more than one element, it is not necessarily a mixture is True. Substances can be classified into two broad categories which are pure substances and mixtures. As defined in the concept hierarchy, a pure substance has a constant composition and uniform properties throughout the sample. This category includes both elements and compounds.
An element is a pure substance made up of one type of atom, and it cannot be broken down into a simpler substance by chemical means. For example, aluminum is an element. A compound is also a pure substance, but it consists of two or more elements that are chemically bonded together. For example, water (H2O) is made up of hydrogen and oxygen atoms that are chemically bonded.
On the other hand, a mixture is a physical combination of two or more elements and/or compounds where the original substances retain their individual properties and can be separated by physical means. Mixtures can be either homogeneous (uniform composition throughout, like salt water) or heterogeneous (non-uniform composition, like sand and iron filings).