A compound differs from a mixture because it:

• A. can have any composition and can always be separated into its components by physical methods
• B. consists of a single type of atom and cannot be decomposed by chemical reactions
• C. has a fixed composition with elements chemically bonded and can be separated only by chemical methods
• D. is always homogeneous, whereas mixtures are always heterogeneous

Answer: (C)

Verified step by step guidance

1. Understand the definitions of compounds and mixtures: A compound is a substance formed when two or more elements are chemically bonded together in a fixed ratio, while a mixture consists of two or more substances physically combined without fixed proportions.
2. Recognize that compounds have a fixed composition, meaning the ratio of elements is constant throughout the substance, whereas mixtures can vary in composition.
3. Note that compounds can only be separated into their constituent elements or simpler compounds by chemical methods (such as chemical reactions), not by physical methods like filtration or distillation.
4. Understand that mixtures can be separated by physical methods because their components retain their individual properties and are not chemically bonded.
5. Conclude that the key difference is that compounds have elements chemically bonded with fixed composition and require chemical methods for separation, while mixtures have variable composition and can be separated by physical methods.