Which of the following describes the term 'mixture'?

The term "mixture" refers to a combination of two or more substances that are physically combined but not chemically bonded. In a mixture, each substance retains its own properties and can be present in varying proportions. This definition encompasses a wide range of combinations, including solids, liquids, and gases, and can include heterogeneous mixtures, where the individual components can be distinguished, as well as homogeneous mixtures, where the components are evenly distributed.

For instance, when you mix sand and salt, both retain their distinct characteristics; this is a classic example of a heterogeneous mixture. If you dissolve salt in water, you create a homogeneous mixture known as a solution, where the individual components are indistinguishable to the naked eye.

The other options do not accurately define a mixture. A combination of elements only limits the definition to elements, excluding compounds or other types of matter. A homogeneous blend specifically refers to mixtures where the components are evenly distributed but does not capture the broader definition of mixtures that can be both homogeneous and heterogeneous. A material containing a single substance describes a pure substance rather than a mixture, which requires at least two components. Thus, the most appropriate definition is indeed the combination of two or more substances.