Question

Four shiny solids are labeled \(A, B, C,\) and \(D\). Given the following information about the solids, deduce the identity of \(\mathrm{A}, \mathrm{B}, \mathrm{C},\) and \(\mathrm{D} .\) (1) The solids are a graphite rod, a silver bar, a lump of "fool's gold" (iron sulfide), and iodine crystals. (2) \(\mathrm{B}, \mathrm{C},\) and \(\mathrm{D}\) are insoluble in water. \(\mathrm{A}\) is slightly soluble. (3) Only C can be hammered into a sheet. (4) \(\mathrm{C}\) and \(\mathrm{D}\) conduct electricity as solids; \(\mathrm{B}\) conducts when melted; A does not conduct as a solid, melted, or dissolved in water.

Short answer

Question: Identify solids A, B, C, and D based on their properties. Answer: A is iodine crystals, B is a graphite rod, C is a silver bar, and D is fool's gold (iron sulfide).

Step-by-step solution

Analyze the solubility of the solids

We know that B, C, and D are insoluble in water and A is slightly soluble. We can use this information to find out which substance A might be: - Graphite: insoluble - Silver: insoluble - Fool's gold (iron sulfide): insoluble - Iodine crystals: slightly soluble Thus, A must be iodine crystals.

Analyze the ability to hammer the solids

We are given that only C can be hammered into a sheet. The property of being able to hammer a substance is called "malleability." From the remaining substances, we can identify the most malleable option: - Graphite: not malleable - Silver: malleable - Fool's gold (iron sulfide): not malleable Thus, C must be a silver bar.

Analyze electrical conductivity

We are given that C and D conduct electricity as solids, B conducts when melted, and A neither conducts as a solid, melted, nor dissolved in water. Since we already identified A as iodine crystals and C as a silver bar, we can analyze the electrical conductivity properties of B and D to determine their identities: - Fool's gold (iron sulfide): conducts as a solid - Graphite: conducts as a solid Thus, D must be fool's gold (iron sulfide) and B must be graphite.

Summarize the identities

Based on the information given and our analysis, we can identify the solids as follows: - A: Iodine crystals - B: Graphite rod - C: Silver bar - D: Fool's gold (iron sulfide)

Key concepts

Solubility

When we talk about solubility, we're referring to the ability of a substance to dissolve in a solvent, like water. In the chemistry problem, solubility helped us determine that substance A, which is slightly soluble, is iodine crystals. This is because out of the given options, iodine is the only one that exhibits this characteristic. A solid's solubility can depend on various factors, such as temperature, pressure, and the nature of both the solute and the solvent.

It's important to note that solubility isn't an all-or-nothing property. Some substances, like the iodine mentioned, are only slightly soluble, meaning they'll dissolve to some extent, but not completely. On the other hand, substances that are insoluble won't dissolve at all in a given solvent under specified conditions. Understanding solubility is essential for many chemistry applications, including medicine, environmental science, and chemical engineering.

Malleability

Malleability is a physical property that refers to a material's ability to be hammered or rolled into thin sheets without breaking. In our problem, only silver (substance C) could be formed into a sheet, making it the malleable substance out of the group. Materials like metals exhibit high malleability due to their particular atomic structure, which allows atoms to slide past each other without breaking the metallic bonds. Silver is well-known for its excellent malleability, making it useful in jewelry, electronics, and as a material for artistic expression.

Why Is Malleability Important?

Malleability is critical in manufacturing and construction since it allows materials to be shaped and customized for various uses. For example, malleable materials are essential in creating car bodies, aircraft parts, and all sorts of everyday items.

Electrical Conductivity

Moving on to electrical conductivity, this property is fundamental in identifying whether substances can conduct electricity. In the given exercise, substances C (silver bar) and D (fool's gold or iron sulfide) were observed to conduct electricity in solid form, which aligns with their known electrical properties. Electrical conductivity is often associated with the presence of free-moving charged particles within a material. For metals, these charged particles are electrons that move relatively freely through the metal's lattice structure.

Applications of Electrical Conductivity

Understanding electrical conductivity is vital in a wide range of fields, from designing electrical components to creating materials that can efficiently generate, transmit, or store electrical energy.

Physical Properties of Solids

Exploring the physical properties of solids like hardness, boiling point, melting point, density, and many others give us valuable insights into how materials will behave in different environments. These properties are inherent to the material's structure and composition. Our chemistry problem called upon a few of these physical properties—specifically solubility, malleability, and electrical conductivity—to deduce the identities of unknown substances.

By understanding and analyzing these properties, we can predict how the material interacts with other substances, how it might be used in applications, and how to manipulate it during manufacturing processes. These foundational characteristics are crucial for scientists and engineers when choosing materials for specific purposes, ensuring that the correct material is used in an appropriate manner to fulfill its intended function.