uniform

A uniform mixture is one where the components are spread so evenly that no individual substance can be picked out, even with a microscope.

• Sugar dissolved in water is the classic example — once stirred in, the sugar particles are distributed so completely that the liquid looks and behaves the same throughout.
• Metals can form uniform mixtures too: stainless steel blends iron, nickel, and chromium so thoroughly that the alloy appears the same all the way through, hiding the individual metals inside it.
• Air counts as a uniform mixture as well — its gases mix so completely that you can't point to where the nitrogen ends and the oxygen begins.
• Being uniform doesn't mean a mixture is pure; it simply means the eye can't tell the components apart, which is very different from a pure substance having only one kind of particle at all.