Question

Classify the following mixtures as homogeneous or heterogeneous. a. gasoline b. a jar of jelly beans c. chunky peanut butter d. margarine e. the paper this question is printed on.

Short answer

a. Gasoline: Homogeneous b. A jar of jelly beans: Heterogeneous c. Chunky peanut butter: Heterogeneous d. Margarine: Homogeneous e. The paper this question is printed on: Heterogeneous

Step-by-step solution

a. gasoline

Gasoline is a homogeneous mixture since its components are uniformly distributed and not visible. It appears as a single phase liquid.

b. a jar of jelly beans

A jar of jelly beans is a heterogeneous mixture because the jelly beans have different colors and flavors, indicating that their components aren't uniformly distributed.

c. chunky peanut butter

Chunky peanut butter is a heterogeneous mixture as it contains visible chunks of peanuts in the mixture, creating an uneven distribution of components.

d. margarine

Margarine is a homogeneous mixture as its components are uniformly mixed, and it appears as a smooth, single-phase substance.

e. the paper this question is printed on

The paper this question is printed on is a heterogeneous mixture because it consists of fibers, fillers, and possibly a watermark distribution in the paper itself, giving it an uneven composition.

Key concepts

Classification of Mixtures

In chemistry, materials can be divided into pure substances or mixtures. Mixtures can be further classified into homogeneous or heterogeneous based on the uniformity of their components. A homogeneous mixture is one where the composition is consistent throughout. Imagine adding sugar to your coffee and stirring until it's completely dissolved; this results in a homogeneous mixture where the sugar is evenly distributed. On the other hand, a heterogeneous mixture contains regions with different properties. An example could be a vegetable soup where the different ingredients are visibly separate from each other.

When we classify substances, it's important to observe their visual characteristics. Homogeneous mixtures, like gasoline, appear uniform because the molecules of the different substances are so thoroughly mixed, they are indistinguishable. With heterogeneous mixtures, such as a jar of jelly beans or chunky peanut butter, the various components, like the colors and pieces of nuts, can be easily discerned.

Physical Properties of Matter

The physical properties of matter include all those characteristics that can be observed without changing the substance into another substance. Basic properties are the state of matter (solid, liquid, or gas), color, smell, and viscosity, among others. For example, gasoline is a liquid that has a very low viscosity, allowing it to flow easily, while margarine is a soft solid with a higher viscosity.

Physical properties are crucial when identifying a substance and determining its use. For instance, the way chunky peanut butter's peanut pieces are scattered in the spread gives it a distinctive texture and consistency, which differ from smooth peanut butter. Similarly, the physical composition of paper, with its fibers and fillers, can affect its texture, strength, and opacity, which are all physical properties important for various applications like printing or writing.

Composition of Mixtures

The composition of mixtures refers to the specific ingredients and quantities present in the mixture. In a homogeneous mixture, the composition is even throughout, which means that any piece of the mixture will have the same proportion of ingredients. Take margarine for example, a spread made to have the same consistency and flavor in every scoop.

In contrast, heterogeneous mixtures such as chunky peanut butter or a jar of jelly beans have an irregular composition. Each scoop of chunky peanut butter might contain a different amount of nuts, and not every handful of jelly beans will contain the same number and variety of flavors. Understanding the composition of mixtures can be important in contexts such as culinary recipes, material manufacturing, and even in scientific research where precise formulations are key.