Which statement best describes compounds?

• A. Compounds can be separated into their components by physical means.
• B. Compounds have variable composition depending on the method of preparation.
• C. Compounds consist of only one type of atom.
• D. Compounds are substances formed by the chemical combination of two or more elements in fixed proportions.

Answer: (D)

Verified step by step guidance

1. Understand the definition of a compound: A compound is a substance formed when two or more elements chemically combine in fixed proportions.
2. Recognize that compounds have a fixed composition, meaning the ratio of elements in a compound is constant regardless of the source or method of preparation.
3. Note that compounds cannot be separated into their elements by physical means; instead, chemical methods are required to break the chemical bonds.
4. Remember that compounds consist of more than one type of atom chemically bonded together, so the statement that compounds consist of only one type of atom is incorrect.
5. Conclude that the best description of compounds is that they are substances formed by the chemical combination of two or more elements in fixed proportions.