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

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 components are evenly distributed (like saltwater), or heterogeneous, where the components are not uniformly distributed (like salad). The properties of mixtures can vary depending on the proportions of their components.

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, milk is considered a heterogeneous mixture because it contains fat globules that can be seen and separated from the liquid, despite appearing uniform at first glance.