Question

State whether each of the following refers to a saturated or unsaturated solution: a. A crystal added to a solution does not change in size. b. A sugar cube completely dissolves when added to a cup of coffee.

Short answer

a. Saturated, b. Unsaturated

Step-by-step solution

Determine the nature of the solution in Scenario A

In scenario (a), a crystal added to a solution does not change in size. This implies that the solution already holds the maximum amount of dissolved substance it can handle at the given temperature and pressure, so no further solute can dissolve. This means the solution is saturated.

Determine the nature of the solution in Scenario B

In scenario (b), a sugar cube completely dissolves when added to a cup of coffee. This implies that the coffee had the capacity to dissolve more sugar, indicating that it had not reached its maximum solubility. Thus, the solution is unsaturated.

Key concepts

Solution Chemistry

Solution chemistry deals with understanding how substances mix to form solutions. A solution is a homogeneous mixture of two or more substances. The substance present in a larger amount is called the solvent, while the substance present in a smaller amount is the solute.

Common examples include salt water (where salt is the solute and water is the solvent) and coffee (where coffee powder is the solute and water is the solvent). By studying solution chemistry, we learn about the properties and behaviors of different solutions. This includes understanding how solutes dissolve in solvents and how factors like temperature and pressure affect this process.

It's important to differentiate between different types of solutions. Solutions can be solid, liquid, or gaseous. Also, they can be classified based on their concentrations, like dilute, concentrated, saturated, and unsaturated solutions.

Saturation

Saturation defines the point at which a solution can hold no more solute at a given temperature and pressure. Think of it as a sponge soaked with water. Once the sponge can no longer absorb more water, it becomes saturated.

Prior to reaching this point, the solution can still dissolve more solute, which means it's unsaturated. However, when you add more solute to a saturated solution and it doesn't dissolve, the solution has reached its saturation limit.

Factors influencing saturation include temperature and pressure:

• Higher temperatures often allow solvents to dissolve more solute, increasing solubility.
• In gases, higher pressure increases solubility in liquids.

These aspects help us understand why solutions behave differently under various conditions and how to manipulate them for practical applications.

Solubility

Solubility is the maximum amount of a solute that can dissolve in a specific amount of solvent at a particular temperature and pressure. Think of solubility as the 'limit' of how much of the solute can be accommodated by the solvent.

Many factors can affect solubility:

• Nature of the solute and solvent: Similar substances dissolve better in each other (like dissolves like).
• Temperature: Higher temperatures generally increase solubility of solids and liquids but decrease solubility of gases.
• Pressure: Mainly affects gases; higher pressure increases the solubility of a gas in a liquid.

Knowing the solubility of a substance helps predict how substances behave in various environments. For example, sugar's high solubility in water makes it ideal for sweetening drinks, while oil's low solubility in water can explain why oil and water don't mix well.

Dissolution Process

The dissolution process describes how a solute dissolves in a solvent to form a solution. This process involves the breakdown of solute molecules and their subsequent interaction with solvent molecules.

Let's break this down:

• First, solute particles separate from the bulk solute. This step usually requires energy.
• Next, the separated solute particles travel into the solvent.
• Finally, the solute particles interact with the solvent molecules and become evenly distributed, creating a homogeneous mixture.

Steps in the dissolution process depend on the nature of the substances involved. In a sugar cube dissolving in coffee, for instance, the sugar molecules break away from the solid form and disperse throughout the coffee.

Temperature, agitation, and the nature of the solute and solvent affect the dissolution rate. Increasing temperature or stirring can speed up the process. That's why hot coffee dissolves sugar cubes faster than cold coffee, and stirring speeds up this effect. Understanding the dissolution process helps in various fields, including drug delivery, environmental science, and everyday cooking and cleaning.