Mixtures
Elementary School
Definition
Combinations of two or more substances that are physically blended but not chemically joined, so each keeps its own properties. Mixtures can be homogeneous, looking the same throughout (like salt water), or heterogeneous, with visibly different parts (like a salad).
Worked examples
Salt water: salt dissolves completely in water, making a clear, uniform solution
A homogeneous mixture — you can't see separate parts, but no chemical bond forms between salt and water.
Trail mix: nuts, raisins, and chocolate chips stay separate and visible
A heterogeneous mixture — each ingredient keeps its own properties and you can pick them apart.
Air: \(78\%\) nitrogen, \(21\%\) oxygen, \(1\%\) other gases blended uniformly
A homogeneous mixture of gases — the molecules stay separate, not chemically bonded.
Common mistakes
- Water (H₂O) is a mixture of hydrogen and oxygen → Water is a compound; hydrogen and oxygen are chemically bonded Mixtures keep each substance's properties; in water the elements combine chemically and lose their original properties.
- All mixtures must be heterogeneous and visibly separated → Mixtures can be homogeneous (uniform) like salt water or heterogeneous like salad Homogeneous mixtures look the same throughout but are still physically blended, not chemically joined.
- You can't separate a mixture once it's mixed → Mixtures can be separated by physical methods like filtering, evaporating, or sorting Because the substances aren't chemically bonded, you can use physical processes to pull them apart.
Where you'll use it next
You'll apply mixtures when studying solutions and concentration, separation techniques like distillation and chromatography, and later in chemistry when comparing physical vs. chemical changes.
See also
Separation MethodsPhysical ChangesStates of MatterSolution PropertiesPhysical PropertiesChemical reaction
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026