Question

Classify each mixture as heterogeneous or homogeneous. (Chapter 3) a. salt water b. vegetable soup c. \(14-\mathrm{Kgold}\) d. concrete

Short answer

a. Salt water: homogeneous b. Vegetable soup: heterogeneous c. \(14-\mathrm{Kgold}\): homogeneous d. Concrete: heterogeneous

Step-by-step solution

a. Salt Water

A homogeneous mixture is a mixture where the components are uniformly distributed and have the same physical properties. In salt water, the salt is evenly distributed within the water, and both components have the same physical properties, making it a homogeneous mixture.

b. Vegetable Soup

A heterogeneous mixture is a mixture where the components are not uniformly distributed and have different physical properties. Vegetable soup is a mixture of different vegetables, broth, and other ingredients that are not uniformly distributed and have different physical properties, making it a heterogeneous mixture.

c. \(14-\mathrm{Kgold}\)

\(14-\mathrm{Kgold}\) is an alloy containing gold and other metals like silver, nickel, or copper. The metals are mixed together so that they are uniformly distributed and have the same physical properties, making it a homogeneous mixture.

d. Concrete

Concrete is a mixture of cement, sand, gravel, and water. The components in concrete are not uniformly distributed, and they have different physical properties, making it a heterogeneous mixture.

Key concepts

Homogeneous Mixtures

In chemistry, homogeneous mixtures have their components mixed so evenly that you can't see the different parts with the naked eye. The term 'homogeneous' means that the mixture is uniform throughout. An easy way to remember this is by thinking of it like blending two colors together completely; you can't see one color or the other—a new, uniform color emerges. Consider salt water as a prime example of this. When salt is dissolved in water, it distributes uniformly, and if you look at a glass of salt water, it appears transparent and constant throughout. Anything taken from one part of the mixture will be the same no matter which part you take it from.
A few key features of homogeneous mixtures include:

• Uniform composition and appearance.
• Cannot be separated by simple physical methods like filtration.
• Consistent physical properties such as boiling point or density.

The important takeaway is that homogeneous mixtures are the same all the way through and appear as one single phase.

Heterogeneous Mixtures

Unlike homogeneous mixtures, heterogeneous mixtures do not have a consistent composition. Imagine a bowl of vegetable soup. You can see, and sometimes separate, the different vegetables and chunks, as they're not evenly distributed throughout. This is what makes it a heterogeneous mixture; the different parts of the mixture are easily recognizable. You may spot pieces of carrots, potatoes, and broth, each displaying their unique properties.
Some key characteristics of heterogeneous mixtures are:

• Varied composition and appearance.
• Components can often be separated by physical methods like sorting and filtration.
• Each part of the mixture maintains its own properties.

Heterogeneous mixtures show us that the ingredients remain distinct rather than merging into one uniform composition.

Alloys

Alloys are fascinating mixtures famous for their importance in crafting metals with desirable properties. They are a type of homogeneous mixture involving metals, where two or more metallic elements are mixed together to improve strength, resistance, or other characteristics. One popular example is 14-karat gold, an alloy made by combining gold with other metals like silver or copper. These metals are blended at the atomic level, which creates a uniform structure enhancing its durability and color for jewelry making.
Here are a few points to remember about alloys:

• Their uniform composition means they are homogeneous.
• Properties typically enhanced by alloying include strength, ductility, and resistance to corrosion.
• Common examples are steel, brass, and bronze.

Alloys are central in industry and crafting because they combine the best properties of the component metals into a more useful hybrid.

Physical Properties of Mixtures

The physical properties of mixtures depend on their composition and can vary widely. These properties include aspects like color, boiling point, and density, and often differ between heterogeneous and homogeneous mixtures. Let's explore how the nature of the mixture impacts these properties.
For homogeneous mixtures:

• They exhibit uniform properties throughout, such as consistent boiling points or density.
• Changes in physical properties are usually global and apply to the entire mixture.

For heterogeneous mixtures:

• The properties can vary from one part of the mixture to another.
• One part of the mixture might be solid, while another part is liquid.

Understanding the physical properties is crucial for identifying and separating mixtures, as each property often tells us something about the mixture's overall structure and behavior.