Question

Classify each of the following as an element, compound, homogeneous mixture, or heterogeneous mixture: (a) copper wire (b) copper ore (c) copper oxide (d) brass alloy

Short answer

(a) Element, (b) Heterogeneous Mixture, (c) Compound, (d) Homogeneous Mixture.

Step-by-step solution

Understand the Definitions

Before classifying the substances, it's essential to understand the definitions. An element is a pure substance consisting of only one type of atom. A compound is a substance formed when two or more elements chemically combine in a fixed ratio. A homogeneous mixture has a uniform composition throughout, whereas a heterogeneous mixture has a non-uniform composition.

Classify Copper Wire

Copper wire is made of pure copper. Since copper is a single type of atom, copper wire is classified as an element.

Classify Copper Ore

Copper ore consists of copper along with other impurities such as different minerals and rocks. As it has a variable composition throughout, copper ore is a heterogeneous mixture.

Classify Copper Oxide

Copper oxide is composed of copper and oxygen chemically combined in a fixed ratio. Therefore, copper oxide is classified as a compound.

Classify Brass Alloy

Brass is a uniform mixture of copper and zinc, where the components are not chemically bonded but are uniformly distributed. Hence, brass is a homogeneous mixture.

Key concepts

Understanding Elements

Elements are the fundamental building blocks in chemistry. They consist of only one type of atom and represent the simplest form of matter. For instance, copper wire is made entirely of copper atoms, which gives it its characteristic properties. In the periodic table, elements are represented as pure substances, and each element has its own unique set of chemical and physical properties.

• Elements cannot be broken down into simpler substances by ordinary chemical means.
• Each element is defined by the number of protons in its atoms, known as the atomic number.

Understanding elements is crucial because they are the basic substances from which compounds and mixtures are formed. Whenever you encounter a pure substance, consider if it is indeed an element by checking if it contains only one type of atom.

Exploring Compounds

Compounds are substances that are formed when two or more elements are chemically bonded together. The bonds between the elements in a compound define its properties. For example, copper oxide is a compound made from copper and oxygen in a fixed ratio. This fixed proportion and chemical bonding distinguish compounds from mixtures.

• Unlike mixtures, compounds have properties different from the individual elements that form them.
• They can only be separated into individual elements by chemical reactions, not by physical processes.

It’s important to recognize that in compounds, the elemental composition is constant. This means that wherever you find a specific compound, the elements are always combined in the same proportion, making them predictably consistent in behavior.

Decoding Mixtures

Mixtures are combinations of two or more substances where each retains its own chemical properties. Mixtures can be categorized into two types: homogeneous and heterogeneous. For instance, brass— a homogeneous mixture (or solution) of copper and zinc. On the other hand, copper ore is a heterogeneous mixture, containing copper among other minerals and rocks.

• In homogeneous mixtures, the composition is uniform, meaning the substances are evenly distributed. Brass is a good example; it appears consistent throughout.
• In heterogeneous mixtures, the composition is not uniform. Different parts can have different compositions, such as copper ore.

Mixtures are different from compounds because the substances in a mixture are not chemically bonded, allowing them to be separated by physical means. Recognizing the type of mixture is essential for studying its properties and potential separation methods.