Determine whether or not each mixture is a solution. (a) sand and water mixture (b) oil and water mixture (c) salt and water mixture (d) sterling silver cup

In chemistry, a 'solution' refers to a special type of homogeneous mixture that is composed of two or more substances. In a solution, the solute is the substance that gets dissolved, while the solvent is the one doing the dissolving. A classic example of a solution is salt dissolved in water: the salt is the solute and water is the solvent.

In our exercise, part (c) the salt and water mixture meets the criteria of a solution because the salt (solute) is completely dissolved in the water (solvent), creating a mixture that is uniform throughout, meaning you cannot distinguish one component from another just by looking at it. On the other hand, sand in water, as stated in part (a), does not dissolve and thus does not form a solution.

Solute-Solvent Interaction

At the molecular level, the interaction between solute and solvent particles is key to understanding solubility. For a substance to dissolve, these particles must interact favorably. This is often summarized by the phrase 'like dissolves like', which means that polar solvents tend to dissolve polar solutes, and nonpolar solvents tend to dissolve nonpolar solutes.

Solubility is a property referring to the ability of a solute to dissolve in a solvent to form a homogeneous mixture. It is quantitatively expressed as the maximum amount of solute that can be dissolved in a specific amount of solvent at a given temperature and pressure.

Solubility plays a crucial role in the creation of solutions. For instance, in the example from the exercise where we looked at a sand and water mixture, we determined that this is not a solution because the sand (solute) has low solubility in water (solvent). Similarly, the oil and water mixture is not a solution because oil's nonpolar molecules are not soluble in water, a polar solvent. Contrarily, salt has high solubility in water, which is why the salt and water mixture is categorized as a solution.

Factors Affecting Solubility

Several factors can influence the solubility of a substance. Temperature is a well-known factor; for many solids dissolved in liquids, increasing the temperature increases solubility. Pressure also plays a role, particularly for gases in liquids—higher pressure increases solubility.

An alloy is a solid solution composed of two or more metals, or a metal and a non-metal. Alloys are created by melting and mixing the components and then allowing the mixture to solidify. Because the atoms of the different elements can be interspersed uniformly throughout the mixture, alloys are considered to be homogeneous mixtures.

In the context of the exercise, sterling silver is an example of an alloy. It's mostly made of silver with some copper added to it. Alloys, including sterling silver, display a uniform distribution of different metal atoms; their properties, however, can be significantly different from those of their component elements. Alloys are typically stronger, harder, or have different melting points compared to pure metals, which is why they are often preferred for making tools, jewelry, and other items.

Properties of Alloys

Due to the mixture of atoms in an alloy, these substances often resist corrosion and have increased strength. The exact properties of an alloy depend on the proportions of the constituent metals and the size and arrangement of their atoms. Some alloys are made to enhance certain characteristics, such as electrical conductivity or resistance to wear, making them invaluable for various industrial applications.