Which term describes any pure substance that cannot be broken down into simpler substances by chemical means?

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

Answer: (A)

In chemistry, the key idea is how a substance can be changed. An element is a pure substance that can’t be broken down into simpler substances by chemical means because it’s made of only one kind of atom. That’s why it’s the correct term here. If something is a compound, it’s composed of two or more elements bonded together and can be decomposed chemically into those elements. A mixture is a physical combination of substances that aren’t chemically bonded, so it isn’t a pure substance. A solution is a kind of homogeneous mixture where a solute is dissolved in a solvent, which also isn’t a pure substance. Examples help: oxygen gas is an element; water is a compound; sea water is a solution; air is a mixture.