Which term best describes a chemical substance formed by combining two or more elements in fixed proportions?

Which term best describes a chemical substance formed by combining two or more elements in fixed proportions?

• A. Compound
• B. Element
• C. Mixture
• D. Solution

Answer: (A)

A compound is a chemical substance formed when atoms of different elements bond together in a fixed ratio. This creates a new substance with its own properties and a definite composition, such as water (two hydrogens and one oxygen). This differs from an element, which is a single kind of atom; a mixture, where substances are just physically combined and can vary in proportion and be separated by physical means; and a solution, which is a homogeneous mixture but still a combination of substances, not a chemically bonded compound. So the substance described—made from two or more elements in fixed proportions—fits the idea of a compound.

A compound is a chemical substance formed when atoms of different elements bond together in a fixed ratio. This creates a new substance with its own properties and a definite composition, such as water (two hydrogens and one oxygen). This differs from an element, which is a single kind of atom; a mixture, where substances are just physically combined and can vary in proportion and be separated by physical means; and a solution, which is a homogeneous mixture but still a combination of substances, not a chemically bonded compound. So the substance described—made from two or more elements in fixed proportions—fits the idea of a compound.