Classify each of the following materials as an element, compound, heterogeneous mixture, or homogeneous mixture:
(a) zinc,
(b) zinc sulfide,
(c) saltwater,
(d) salad.
The correct answer and explanation is :
Let’s classify each material:
(a) Zinc: Element
(b) Zinc sulfide: Compound
(c) Saltwater: Homogeneous mixture
(d) Salad: Heterogeneous mixture
Explanation:
- Zinc (Zn):
Zinc is classified as an element because it consists of only one type of atom. Elements are pure substances that cannot be broken down further by chemical means. Zinc has the atomic number 30 on the periodic table, meaning each zinc atom contains 30 protons in its nucleus. Elements can be metals, nonmetals, or metalloids, and zinc is a metal. - Zinc sulfide (ZnS):
Zinc sulfide is a compound, as it is made up of two different elements—zinc (Zn) and sulfur (S)—chemically bonded together. Compounds are substances that contain two or more elements that are chemically combined in fixed proportions. In zinc sulfide, the zinc and sulfur atoms form a stable bond, and it can only be separated into zinc and sulfur through chemical reactions, such as heating or using a chemical reagent. - Saltwater (NaCl in water):
Saltwater is a homogeneous mixture, meaning the composition is uniform throughout. A homogeneous mixture is a mixture where the individual components are evenly distributed and indistinguishable from one another. In saltwater, salt (sodium chloride, NaCl) dissolves completely in water, forming a solution where the salt is evenly distributed throughout the water. The different components (salt and water) are not chemically bonded, and you can separate them by evaporating the water. - Salad:
A salad is a heterogeneous mixture because its components are not uniformly mixed, and the individual parts can be distinguished from one another. Heterogeneous mixtures have varying compositions throughout. In a salad, you can see and pick out individual ingredients, such as lettuce, tomatoes, cucumbers, and dressing. These ingredients retain their individual properties and can be physically separated.
In summary:
- Element: Pure substance made of only one type of atom (Zinc).
- Compound: A substance formed by chemical bonding of two or more different elements (Zinc sulfide).
- Homogeneous mixture: A mixture with a uniform composition (Saltwater).
- Heterogeneous mixture: A mixture with components that are not uniformly distributed (Salad).