What is a key feature of compounds as compared to mixtures?

A key feature of compounds is that they form with a specific ratio of elements. This characteristic is essential to the definition of a compound, as it indicates that the elements are chemically bonded in a definite proportion by mass. For example, water (H₂O) always consists of two hydrogen atoms and one oxygen atom, maintaining that specific ratio regardless of the amount present or its state of matter. This stability in composition is what distinguishes compounds from mixtures, where the components can vary in proportion and do not have fixed ratios.

In contrast, while mixtures can indeed consist of different substances that retain their individual properties, compounds exhibit distinct properties that arise from the chemical bonds formed between the elements. Understanding this idea is crucial for anyone studying the principles of chemistry and its applications in hair coloring, where precise formulations are often required for consistent results.