Final answer:
The statement that correctly describes compounds is that they are substances with a fixed composition, different properties from their constituent elements, and cannot be physically separated into their elements.
Step-by-step explanation:
The correct answer to the question which states "Which statement accurately describes compounds?" is option b) They are substances. Compounds are substances that contain two or more elements chemically combined in a fixed proportion. They have a unique composition and possess definite chemical and physical properties. The properties of a compound are generally different from the properties of the elements it contains.
For example, water (H₂O) is a compound made up of two elements: hydrogen and oxygen. The water molecule is always made up of two atoms of hydrogen and one atom of oxygen, which indicates a fixed proportion. Additionally, the properties of water are very different from either of its constituent elements. Water is a fluid at room temperature, while oxygen is a gas, and hydrogen is a highly flammable gas. When hydrogen and oxygen combine, they form a stable liquid that is essential for life, which is characteristic the two elements do not possess individually.
It is also important to note that compounds cannot be separated into their components by physical means, and they do not vary in composition. Furthermore, a compound does not exhibit the properties of its component elements; it behaves as a completely different substance.