Examples of mixtures in everyday life
A mixture contains two or more substances that are physically combined but not chemically bonded, so each keeps its own properties. The proportions can vary, and the parts can usually be separated by physical methods such as filtering, evaporating or using a magnet. Most things in daily life, from the air you breathe to the food you eat, are mixtures.
- Air — a homogeneous mixture of about 78% nitrogen, 21% oxygen, 1% argon and traces of other gases.
- Salt water — salt dissolved evenly in water; evaporating the water gets the salt back.
- Sand and iron filings — a heterogeneous mixture you can separate with a magnet.
- Concrete — gravel and sand held together by cement, with the separate pieces easy to see.
- Milk — tiny droplets of fat and particles of protein spread through water (a colloid).
- Soil — minerals, organic matter, water and air mixed unevenly.
- Blood — red cells, white cells and platelets suspended in liquid plasma.
- Trail mix — nuts, raisins and chocolate you can pick apart by hand.
- Salad — vegetables that each keep their own color, taste and texture.
- Orange juice with pulp — bits of fruit floating in a sweet, watery liquid.
- Vinegar — acetic acid dissolved in water, usually about 5% acid.
- Brass — a solid mixture (alloy) of copper and zinc.
- Gasoline — a blend of many different hydrocarbons, plus additives.
- Smoke — tiny solid particles and gases spread through air.
- Fog — tiny droplets of liquid water suspended in air (a colloid).
- Soda — carbon dioxide, sugar or sweeteners and flavorings dissolved in water.
- Granite — a rock made of visible grains of quartz, feldspar and other minerals.
- Oil and vinegar dressing — separates into two layers if left to stand.
- Muddy water — soil particles that slowly settle to the bottom (a suspension).
- Mayonnaise — oil droplets spread through vinegar or lemon juice, kept stable by egg yolk (an emulsion).
Homogeneous or heterogeneous?
In a homogeneous mixture, also called a solution, the parts are blended so evenly that every sample looks and behaves the same, as in air, salt water or brass. In a heterogeneous mixture, such as soil or a salad, you can see the different parts. Colloids such as milk and fog look uniform, but their particles are large enough to scatter light, so they are usually classed as heterogeneous.
How mixtures are separated
Because the parts are not chemically bonded, mixtures can be separated using differences in physical properties. Filtering separates solids from liquids, evaporation and distillation use differences in boiling point, magnets pull out iron, and chromatography separates dissolved substances such as the dyes in ink.