Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous: (a) air, (b) tomato juice, (c) iodine crystals, (d) sand.
The Correct Answer and Explanation is:
ChatGPT said:
Here are the classifications:
- (a) Air – Mixture (Homogeneous)
- (b) Tomato juice – Mixture (Heterogeneous)
- (c) Iodine crystals – Pure substance
- (d) Sand – Mixture (Heterogeneous)
Explanation
Matter can be broadly classified into pure substances and mixtures. A pure substance is composed of only one type of particle and has a fixed composition and definite properties. It can be an element (like iodine) or a compound (like water). In contrast, a mixture contains two or more substances physically combined and can vary in composition.
Air is a homogeneous mixture. It is composed of nitrogen, oxygen, carbon dioxide, and trace gases, all uniformly mixed. Even though it looks like a single substance, it’s actually a blend of different gases, making it a mixture. Since the composition is uniform throughout, it’s classified as homogeneous.
Tomato juice is a heterogeneous mixture. While it might appear uniform at a glance, it contains suspended solids such as pulp and seeds. These particles are not evenly distributed and can settle over time, which breaks the uniformity of the mixture. Thus, tomato juice is heterogeneous.
Iodine crystals are a pure substance. Iodine is a chemical element (symbol I), and its crystals consist entirely of iodine molecules. The composition is consistent throughout, without any physical blending of different substances, which classifies it as a pure substance.
Sand is a heterogeneous mixture. While it may look uniform in color or texture, it typically consists of particles of different minerals and materials, such as quartz, feldspar, and organic matter. These are not uniformly mixed at the molecular level, and differences can be observed even by the naked eye, making sand a heterogeneous mixture.
In conclusion, recognizing whether a sample is a pure substance or a mixture—and if a mixture, whether it’s homogeneous or heterogeneous—requires examining its composition and the uniformity of its components.
