Which term describes a substance with a fixed composition made from one kind of material?

• A. Element
• B. Pure Substance
• C. Compound
• D. Mixture

Answer: (B)

A substance with a fixed composition and uniform properties is a pure substance. That means it’s made from only one kind of material, so every sample has the same makeup and cannot be separated into different substances by simple physical means. The term that describes this idea is pure substance. It’s also helpful to know that pure substances include elements (made of one kind of atom) and compounds (two or more elements in a fixed ratio). Mixtures, by contrast, have variable composition and can be separated into different substances, which is why they are not described as pure substances.