Classify each of the following as a pure substance, a solution, or a heterogeneous mixture: b. a cup of coffee

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Understand the definitions: A pure substance has a uniform and definite composition, a solution is a homogeneous mixture where the components are uniformly distributed, and a heterogeneous mixture has visibly different substances or phases.

Consider the composition of a cup of coffee: It typically contains water, dissolved coffee compounds, and possibly other ingredients like sugar or milk.

Determine if the components are uniformly distributed: In a typical cup of black coffee, the dissolved coffee compounds are evenly distributed throughout the liquid.

Evaluate if there are any visible different substances or phases: In black coffee, there are no visible separate phases; it appears uniform throughout.

Classify the cup of coffee: Since the components are uniformly distributed and there are no visible different phases, a cup of black coffee is best classified as a solution.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Pure Substance

A pure substance consists of a single type of particle and has a uniform composition throughout. It can be an element, like oxygen, or a compound, like water. Pure substances have consistent physical and chemical properties, making them distinct from mixtures.

Solution

A solution is a homogeneous mixture where one substance (the solute) is dissolved in another (the solvent). The components of a solution are evenly distributed at the molecular level, resulting in a single phase. An example is saltwater, where salt is completely dissolved in water.

Heterogeneous Mixture

A heterogeneous mixture contains two or more substances that remain distinct and can be physically separated. The components are not uniformly distributed, leading to different phases or layers. An example is a salad, where the individual ingredients can be seen and separated.

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