What is a mixture that looks like a pure substance?

Matter can be broken down into two categories: pure substances and mixtures. Pure substances are further broken down into elements and compounds. Mixtures are physically combined structures that can be separated into their original components. A chemical substance is composed of one type of atom or molecule.

In the more general sense, a pure substance is any homogeneous mixture. That is, it is matter that appears uniform in appearance and composition, no matter how small the sample size. Examples of pure substances include iron, steel, and water. Air is a homogeneous mixture that is often considered to be a pure substance.

In chemistry, a pure substance is a sample of matter with both definite and constant composition and distinct chemical properties. To avoid confusion, a pure substance is often referred to as a "chemical substance."

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