IB Chemistry Standard Level (SL) Practice Exam

A solution is defined as a homogeneous mixture of two or more substances, where the components are uniformly distributed throughout the mixture. This means that in a solution, the composition is consistent and the individual substances, such as solute and solvent, cannot easily be distinguished from one another. For example, when salt is dissolved in water, the salt and water form a clear liquid with the solute evenly dispersed at the molecular level, creating a uniform appearance. In contrast, the other options do not accurately describe a solution. A heterogeneous mixture involves distinct components that can be seen and may settle over time, such as oil and water. A single element in its pure form does not constitute a mixture but rather a specific type of substance, which would not be classified as a solution. Lastly, a new chemical compound formed by a reaction denotes a chemical change resulting in substances with different properties from the reactants, which is not characteristic of the physical blending that occurs in a solution. Therefore, defining a solution as a homogeneous mixture correctly encapsulates its essential characteristics.