Which term matches the definition: a uniform substance made up of only one type of particle, which can be an element or a compound?

Which term matches the definition: a uniform substance made up of only one type of particle, which can be an element or a compound?

• A. Mixture
• B. Solution
• C. Pure substance
• D. Phase

Answer: (C)

Pure substance. A pure substance is a uniform material made of only one type of particle, which can be an element or a compound. If it’s an element, all the particles are the same atoms (like helium). If it’s a compound, the particles are identical molecules composed of the same atoms in a fixed ratio (like water, H2O). This fixed, single-type composition gives pure substances well-defined properties. Mixtures, even when they look uniform, contain more than one type of particle (for example, a solvent plus dissolved solute in a solution), so they aren’t pure substances. A phase describes a state of matter (solid, liquid, gas) rather than the composition being a single particle type.

Pure substance. A pure substance is a uniform material made of only one type of particle, which can be an element or a compound. If it’s an element, all the particles are the same atoms (like helium). If it’s a compound, the particles are identical molecules composed of the same atoms in a fixed ratio (like water, H2O). This fixed, single-type composition gives pure substances well-defined properties. Mixtures, even when they look uniform, contain more than one type of particle (for example, a solvent plus dissolved solute in a solution), so they aren’t pure substances. A phase describes a state of matter (solid, liquid, gas) rather than the composition being a single particle type.