Mixture Facts for Kids

In chemistry, a mixture is when you put two or more different things together. These things can be simple chemical elements, like oxygen, or compounds, like water. Mixtures can be made of liquids, solids, or even gases.

A mixture is different from a compound. A compound is made when two or more atoms join together chemically. For example, a mixture of hydrogen gas and nitrogen gas just contains hydrogen and nitrogen. It's not the same as ammonia, which is a compound made from hydrogen and nitrogen atoms joined together.

Sometimes, you can easily see the different parts in a mixture. This is called a heterogeneous mixture. If you can't tell the parts apart, it's a homogeneous mixture. A third type is called a colloid.

When one substance in a mixture completely dissolves into another, it forms a solution. Think about putting sugar in water. First, it's a mixture, then the sugar dissolves to make a solution. If a substance doesn't dissolve, it's called a suspension.

Even solids can be mixtures! Alloys, like bronze or steel, are mixtures of different metals. Many types of soil and rock are also mixtures of various minerals. So, a mixture is just two or more elements or compounds that are mixed, but not chemically joined.

What Makes Mixtures Special?
Types of Mixtures You See Every Day
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What Makes Mixtures Special?

Mixtures have some cool features that help us tell them apart from compounds. You can usually separate the parts of a mixture using simple physical methods.

How to Separate Mixtures

You can separate the parts of a mixture using physical ways. This means you don't need a chemical reaction. Some common methods include:

Filtration: Like using a coffee filter to separate coffee grounds from liquid coffee.
Freezing: If one part freezes before another, you can separate them.
Distillation: Heating a liquid mixture to turn one part into a gas, then cooling it back into a liquid.
Gravity: Letting heavier parts settle to the bottom.
Centrifugation: Spinning a mixture very fast to separate parts based on their density.

Mixtures Keep Their Properties

When you mix things, they usually keep their own properties. For example, if you mix sand and water, the sand is still sand, and the water is still water. Neither one changes what it is. The sand still feels gritty, and the water is still wet.

Mixtures Have Flexible Recipes

Mixtures can have different amounts of their parts. You can make a weak sugar solution with a little sugar or a very sweet one with a lot. Compounds, however, always have a fixed recipe. Water is always H₂O, never H₃O or HO.

No Big Energy Changes

When a mixture forms, there's usually not much energy given off or taken in. This is different from when compounds form, which often involves a lot of energy change.

Types of Mixtures You See Every Day

Mixtures can be made from any combination of solids, liquids, and gases. Here are some common examples:

Gas in Gas: The air we breathe is a great example. It's a mixture of oxygen, nitrogen, and other gases.
Liquid in Gas: Think of fog or mist. These are tiny liquid water droplets floating in the air.
Solid in Gas: Smoke is a mixture of tiny solid particles floating in gas.
Gas in Liquid: The oxygen dissolved in water that fish breathe is a solution. Also, the bubbles in whipped cream are gas mixed into a liquid.
Liquid in Liquid: Alcoholic beverages are often mixtures of alcohol and water. Milk and mayonnaise are examples of emulsions, where tiny liquid droplets are spread throughout another liquid.
Solid in Liquid: When sugar dissolves in water, it's a solution. Mud is a suspension of soil particles in water. Blood is a colloid with different cells and proteins mixed in liquid plasma.
Gas in Solid: Styrofoam is a solid foam with gas trapped inside.
Liquid in Solid: Gelatin is a gel, where a liquid is spread throughout a solid.
Solid in Solid: Alloys like brass (copper and zinc) are solid solutions. Granite is a mixture of different solid minerals.