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

Verified step by step guidance

1. Understand the definitions: A pure substance has a uniform and definite composition, while a mixture contains two or more substances physically combined. A homogeneous mixture has a uniform composition throughout, whereas a heterogeneous mixture has a non-uniform composition.
2. Consider the composition of milk: Milk is composed of water, fats, proteins, lactose, minerals, and vitamins.
3. Determine if milk is a pure substance or a mixture: Since milk contains multiple components that are physically combined, it is a mixture.
4. Assess the uniformity of milk: Milk appears uniform to the naked eye, indicating that it is a homogeneous mixture.
5. Conclude the classification: Milk is a homogeneous mixture because its composition is uniform throughout.

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.