What type of change do mixtures involve?

Mixtures involve physical changes. When substances are combined to form a mixture, they maintain their individual properties and can be separated by physical means without altering their chemical composition. For instance, when sand and salt are mixed together, each substance retains its distinctive characteristics, and they can be separated by dissolving the salt in water and filtering the sand out. This process does not involve any chemical reaction but rather a physical combination of materials.

In contrast, chemical changes involve a transformation that alters the composition of the substances, resulting in new substances being formed, often accompanied by changes in energy. Biological changes typically relate to living organisms, involving metabolic processes or life cycles. Thermal changes would refer to temperature fluctuations that can impact both chemical and physical processes, but they are not the primary consideration when discussing mixtures. Thus, the correct attribute associated with mixtures is their formation through physical changes.