A pure substance has been isolated in the laboratory. Based on the two characteristics below, how can the substance be classified?
I. The species cannot be separated by physical means.
II. The species can be separated by chemical means.
A) an element
B) a compound
C) a homogeneous mixture
D) a heterogeneous mixture
The correct answer and explanation is :
The correct answer is B) a compound.
Explanation:
To classify the isolated substance, we need to understand the key characteristics provided and how they relate to the types of substances in chemistry.
I. The species cannot be separated by physical means.
- This statement suggests that the substance is not a mixture. In mixtures, the individual components retain their own properties and can usually be separated by physical methods such as filtration, distillation, or centrifugation. A pure substance, on the other hand, cannot be separated into its components by physical means. This rules out mixtures (both homogeneous and heterogeneous), leaving us with either an element or a compound.
II. The species can be separated by chemical means.
- This statement is crucial. It indicates that the substance is a compound, which is a chemical combination of two or more elements. Compounds can be broken down into their constituent elements or simpler compounds only by chemical means, such as through a chemical reaction. This is a key characteristic distinguishing compounds from elements. Elements cannot be separated into simpler substances by chemical means; they are in their most basic form and consist of only one type of atom.
Now let’s break down the choices:
- A) An element: Elements are pure substances made of only one type of atom. They cannot be broken down into simpler substances by chemical means. Since the species in the problem can be separated by chemical means, it cannot be an element.
- B) A compound: Compounds are pure substances composed of two or more different elements chemically bonded. They can only be separated into their constituent elements through chemical reactions (e.g., electrolysis of water into hydrogen and oxygen). Given that the species can be separated by chemical means, this is the correct classification.
- C) A homogeneous mixture: Homogeneous mixtures consist of two or more substances that are uniformly mixed, and the components can usually be separated by physical methods (e.g., evaporation, filtration). This option is incorrect because the substance cannot be separated by physical means.
- D) A heterogeneous mixture: Heterogeneous mixtures contain visibly distinct components that can be physically separated. This option is also incorrect because the substance described cannot be separated by physical means.
Thus, based on the characteristics provided, the substance can be classified as B) a compound, since compounds can only be separated by chemical methods.