Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous: (d) sawdust.

Key Concepts

Pure Substances

A pure substance consists of a single type of particle and has a uniform composition throughout. Examples include elements like oxygen and compounds like water. Pure substances have distinct physical and chemical properties that do not change regardless of the sample size.

Mixtures

Mixtures are combinations of two or more substances that retain their individual properties. They can be classified as homogeneous, where the composition is uniform (like saltwater), or heterogeneous, where the composition is not uniform (like a salad). The components in a mixture can often be separated by physical means.

Homogeneous vs. Heterogeneous Mixtures

Homogeneous mixtures have a consistent composition throughout, making it difficult to distinguish the individual components, while heterogeneous mixtures contain visibly different substances or phases. For example, a solution of sugar in water is homogeneous, whereas a mixture of sand and iron filings is heterogeneous, as the individual components can be seen and separated.