Question

A dry cleaning solvent contains chlorofluorocarbons (CFCs). Is this dry cleaning solvent an example of a homogeneous mixture or a pure substance?

Short answer

The dry cleaning solvent is a homogeneous mixture.

Step-by-step solution

Understand the Components

A dry cleaning solvent containing chlorofluorocarbons (CFCs) is mentioned. This indicates the solvent contains multiple components as it has specific chemicals like CFCs.

Determine the Type of Mixture or Substance

A pure substance has uniform and consistent properties throughout and consists of only one type of particle. In contrast, a homogeneous mixture also has uniform composition, but it contains multiple different substances mixed together.

Identify Characteristics of the Solvent

The solvent containing CFCs has multiple substances blended uniformly, indicating that no matter which part of the solvent you analyze, the composition remains consistent, showcasing homogeneous properties.

Conclusion Based on Definitions

Since the solvent contains multiple substances that are evenly distributed throughout, it fits the definition of a homogeneous mixture rather than a pure substance.

Key concepts

Understanding Chlorofluorocarbons

Chlorofluorocarbons, often abbreviated as CFCs, are compounds made up of chlorine, fluorine, and carbon. These were widely used in the past for various industrial applications, due to their stability and non-flammable properties. However, CFCs gained infamy because of their environmental impact, particularly their role in depleting the ozone layer. This led to global agreements to phase them out under regulations like the Montreal Protocol.
While they are no longer as prevalent, CFCs still appear in certain specialized applications and chemical mixtures. These can be vital for understanding the nature of different substances, such as when identifying whether a solvent is a pure substance or a mixture.
Recognizing the presence of CFCs in a substance, like a dry cleaning solvent, can help in understanding its composition. In most cases, the presence of CFCs indicates that the solvent isn't pure, since CFCs themselves are compounds made of more than one type of atom.

Role of Solvents in Mixtures

A solvent is a substance that dissolves a solute, creating a solution. Solvents are an essential component in many chemical processes, serving as vehicles to transport and mix other substances.
In the case of the dry cleaning solvent in the exercise, its primary role is to dissolve and remove stains or contaminants from fabrics. These solvents can be composed of a single type of molecule or a blend of different substances.

• Many solvents, like those used in dry cleaning, are not pure substances. They often rely on mixtures to achieve desired functional properties, like cleaning efficiency.
• They can be tailored to have a specific balance of components, including additives like CFCs, which ensure the solvent operates effectively.

Such a combination of substances creates a homogeneous solution, where the different constituents are mixed evenly throughout, presenting no visible separation.

Defining Pure Substances

A pure substance is any material that contains only one type of particle or component. This means that throughout the entire sample of the substance, its composition is consistent and does not vary.
Pure substances can either be elements or compounds. For example:

• Elements, like gold or oxygen, consist of only one type of atom.
• Compounds, such as water or carbon dioxide, are formed from two or more types of atoms bonded together, but still exist as a single kind of particle through the sample.

This uniformity is critical to the definition of a pure substance, distinguishing it from mixtures, which can contain multiple different types of particles, even if they appear consistent to the eye.

Characteristics of Mixture Properties

Mixtures are fascinating because they consist of two or more substances that are physically combined, rather than chemically bonded. There are two primary types of mixtures: homogeneous and heterogeneous.
Homogeneous mixtures, like the solvent containing CFCs described in the exercise, have components that are evenly distributed throughout. This makes them appear uniform at the macroscopic level, so any sample taken from the mixture will have the same composition.

• An example of a homogeneous mixture is saltwater, where salt is thoroughly dissolved in water, resulting in a consistent taste and appearance.
• Heterogeneous mixtures, on the other hand, have a non-uniform composition with distinct parts that are visibly separate, like a salad, where you can see each ingredient individually.

Understanding these properties is crucial when classifying substances and predicting their behavior in various applications, like those in cleaning solutions.