What distinguishes a compound from a mixture of elements?

A compound is defined as a substance formed when two or more elements are chemically combined in a fixed ratio, resulting in new properties that differ from those of the individual elements. This means that a compound does not exhibit the individual properties of its components; instead, it possesses unique characteristics that arise from the chemical bonding between the elements.

For instance, water (H₂O) is a compound created from hydrogen and oxygen. While hydrogen is a flammable gas and oxygen supports combustion, the compound water does not exhibit these properties. Instead, it serves as a liquid at room temperature with distinct physical and chemical properties useful in many contexts.

In contrast, a mixture consists of two or more substances that are physically combined, and it retains the properties of each component. Therefore, the properties of the mixture can still be attributed to its individual elements.

The other options highlight characteristics that are not accurate representations of the differences between mixtures and compounds. A compound typically cannot be separated into its elements through physical means; such separation generally requires chemical reactions. Mixtures do not involve elements that are chemically bonded, and the distinction in how compounds do not exhibit individual properties reinforces the central nature of what defines a compound versus a mixture.