Question

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.

Short answer

(a) Air: Homogeneous mixture. (b) Tomato Juice: Heterogeneous mixture. (c) Iodine Crystals: Pure substance. (d) Sand: Heterogeneous mixture.

Step-by-step solution

(a) Air

: Air is a mixture of various gases, such as nitrogen, oxygen, carbon dioxide, and small amounts of other gases. Its composition is uniform throughout, making it a homogeneous mixture.

(b) Tomato Juice

: Tomato juice is a mixture that consists of water, tomato pulp, and other ingredients like salt and sugar. Although the juice may appear uniform, it contains tiny suspended particles of tomato solids, which can settle or separate out over time. Thus, tomato juice is a heterogeneous mixture.

(c) Iodine Crystals

: Iodine crystals are a form of elemental iodine and are made up of single, repeating type of iodine molecules (I2). As it consists of only one type of element with a consistent composition, iodine crystals are classified as a pure substance.

(d) Sand

: Sand is a mixture of various minerals, rock fragments, and other particles, such as shells or organic matter. These components have different sizes, colors, and compositions, making the mixture non-uniform in appearance and composition. Therefore, sand is a heterogeneous mixture.