Question

Classify the following as solution or heterogeneous mixture. (a) maple syrup (b) seawater passed through a sieve (c) melted rocky road ice cream

Short answer

Question: Determine whether each example is a solution or a heterogeneous mixture: (a) Maple syrup, (b) Seawater passed through a sieve, (c) Melted rocky road ice cream. Answer: (a) Maple syrup is a solution, (b) Seawater passed through a sieve is a solution, (c) Melted rocky road ice cream is a heterogeneous mixture.

Step-by-step solution

(a) Maple syrup

Maple syrup is made primarily of water and sucrose (sugar), with small amounts of other substances. In this mixture, the sugar is dissolved evenly throughout the water, making it a homogeneous mixture with a uniform composition. Additionally, there are no visible phases or sections with distinct properties. Therefore, maple syrup is considered a solution.

(b) Seawater passed through a sieve

When seawater passes through a sieve, solid particles and other impurities are removed. However, the dissolved salts and other substances in the water are still evenly distributed throughout the water, creating a uniform composition. Therefore, sieving does not change the fact that seawater is a homogeneous mixture of water and dissolved substances like salts and minerals. As a result, seawater passed through a sieve is considered a solution.

(c) Melted rocky road ice cream

Rocky road ice cream is a combination of ice cream, nuts, and marshmallows. When this mixture is melted, the different components (ice cream, nuts, and marshmallows) don't dissolve evenly into one another. Instead, they form a mixture with separate, visible phases or sections with distinct properties. Therefore, melted rocky road ice cream is considered a heterogeneous mixture.

Key concepts

Solution

A solution is a type of mixture where two or more substances are uniformly distributed at the molecular level. It typically consists of a solute, which is the substance that is dissolved, and a solvent, the substance in which the solute is dissolved. Common examples like salt water, where salt is the solute dissolved in water, the solvent, allow us to observe properties like clarity and uniformity.

Solutions are characterized by their uniform composition, meaning that the concentration of solute is consistent throughout the solution. They don't have visible phases because the mixture presents a single phase where the components are indistinguishable from each other even under magnification, such as maple syrup or sieved seawater, as discussed in the textbook examples.

Heterogeneous Mixture

Unlike solutions, heterogeneous mixtures have a non-uniform composition and often contain visible phases or parts that are clearly different from one another. The individual substances within a heterogeneous mixture retain their properties and can often be separated by simple physical means. These mixtures can include solids, liquids, and gases in various combinations.

A classic instance of a heterogeneous mixture is melted rocky road ice cream. As it melts, the distinctive parts such as nuts and marshmallows do not blend uniformly with the liquid phase of the cream. Instead, you can see separate areas where the different ingredients congregate, each retaining its unique properties and appearance.

Uniform Composition

Uniform composition is a definitive feature of a solution. It suggests that all parts of the mixture are consistent, and any sample taken from the mixture will have the same composition and properties. For a better grasp of this concept, picture stirring a spoonful of sugar into water. Once the sugar has dissolved fully, no matter where you sample the liquid, the sweetness will be evenly distributed.

The significance of uniform composition becomes clear when considering substances for various uses such as cooking or chemical reactions; the expected outcome relies on consistent properties throughout the solution.

Visible Phases

Visible phases are the different parts of a mixture that can be seen with the naked eye. They are indicative of a heterogeneous mixture. For example, in the exercise example of melted rocky road ice cream, the ice cream base, the nuts, and marshmallows would create distinct layers or chunks—each visible and separate from one another.

Recognizing visible phases is critical when determining if a mixture is homogeneous or heterogeneous. The absence of these distinct parts signifies a homogeneous mixture, where the dissolved substance cannot be seen separate from the solvent, resulting in no visible phases.