Problem 39 - Introductory Chemistry Atoms First

Question

Both a soft drink and the atmosphere we breathe are properly called solutions. For each, state why this is true, and also state the solvent for each.

Step-by-Step Solution

Answer

Both a soft drink and the atmosphere are considered solutions because they are homogeneous mixtures of different components. A soft drink is a mixture of water, sugar, flavorings, and carbon dioxide gas, appearing as a single-phase liquid with gas bubbles. The atmosphere is a mixture of nitrogen, oxygen, carbon dioxide, and trace amounts of other gases, appearing as a single-phase gaseous mixture. In a soft drink, the solvent is water, while in the atmosphere, the solvent is nitrogen gas (N2).

Step 1: Understanding Solutions

A solution is a homogeneous mixture of two or more substances, in which one substance (the solute) is uniformly distributed within the other (the solvent). In a solution, the solute dissolves into the solvent, resulting in a single-phase mixture.

Step 2: Soft Drink as a Solution

A soft drink is a solution because it is a homogeneous mixture of various components, such as water, sugar, flavorings, and carbon dioxide gas. These components are uniformly mixed, and the soft drink appears as a single-phase liquid with gas bubbles.

Step 3: Solvent in a Soft Drink

The solvent in a soft drink is water. Water acts as the dissolving medium for sugar, flavorings, and other components present in the soft drink.

Step 4: Atmosphere as a Solution

The atmosphere is also considered a solution because it is a homogeneous mixture of various gases, such as nitrogen, oxygen, carbon dioxide, and trace amounts of other gases. These gases are uniformly mixed in the atmosphere, and it appears as a single-phase gaseous mixture.

Step 5: Solvent in the Atmosphere

The solvent in the atmosphere is nitrogen gas (N2), which makes up approximately 78% of the air we breathe. Nitrogen acts as the dissolving medium for the other gases present in the atmosphere, such as oxygen and carbon dioxide.

Key Concepts

Homogeneous Mixtures

When we talk about solutions in chemistry, what we're really referring to are homogeneous mixtures. By definition, a mixture is 'homogeneous' when its components are uniformly distributed throughout the substance. This means that, no matter how small a sample you take from the mixture, its composition will be the same as that of any other sample. A soft drink exemplifies this perfectly.

It's hard to imagine, but that fizzy beverage is a scientific marvel of consistent taste because each sip contains the same proportion of water, sugar, flavorings, and carbon dioxide. Now, looking at the atmosphere, we see a much larger, boundless example of a homogeneous mixture. Just like in a soft drink, the various gases such as nitrogen, oxygen, and carbon dioxide are mixed so well that every breath we take has the same proportion of these gases, providing a constant experience regardless of where we are (at least within the breathable layers of the atmosphere).

Solute and Solvent

At the heart of any solution, we find two key players: the solute and the solvent. The solute is the substance that dissolves, and the solvent is the substance that does the dissolving. They come together to form the solution, where the solute distributes evenly throughout the solvent.Take the soft drink again, for example. Sugar and flavorings are solutes, vanishing seamlessly into water, the solvent, which in turn carries them throughout the entire drink. It's like a magical disappearing act where the solutes transform from their original form into a uniform distribution within the solvent.

In the case of our atmosphere, the most abundant gas, nitrogen, serves as the solvent, with other gases such as oxygen and carbon dioxide playing the role of solutes. Despite gases being invisible to our eyes, they dissolve into one another, much like sugar does in water, creating a uniform mixture that we experience with every inhale and exhale.

Physical States of Solutions

Solutions come in various physical states—gas, liquid, and solid—and it's an incredible display of chemical versatility. Most often, when people think of solutions, they picture a liquid. However, solutions can take form in any state of matter.

A soft drink is a classic liquid solution, formed as various solutes like sugar and carbon dioxide dissolve in water. But not all solutions are so visible or even so tangible. The air around us is a gaseous solution, composed of different gases mingling together so well that we only notice them indirectly, such as when the wind blows.

Even solid solutions exist, such as alloys, where metals are mixed together to create a uniform solid that retains the properties of both individual substances. The key takeaway is that solutions can be formed in any state, and their behavior and principles remain consistent across these different physical experiences.