Mixing It Up
Upper Elementary · Physical Science · Mixtures
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A Prediction Experiment

Mixing It Up

When you stir two things together you make a mixture — but some mixtures vanish into a clear liquid and others stay lumpy. Today you'll learn the difference, then you will predict what each mixture does.

Before we start — stir sugar into water and it vanishes; stir in sand and it doesn't — why the difference?

A mixture is just things mixed

A mixture is two or more things physically mixed together — not chemically joined. Each thing keeps its own properties, and you can separate them again (unlike when atoms react to make a brand-new substance).

Quick check, together: In a mixture, are the parts chemically joined into something new, or just mixed together?
Answer: Just mixed together — each part keeps its properties and can be separated again.

When it dissolves: a solution

If one thing dissolves evenly into another, you get a solution. The thing that dissolves is the solute (like salt); the thing it dissolves into is the solvent (like water).

Quick check, together: In salt water, which part is the solute and which is the solvent?
Answer: Salt is the solute (it dissolves); water is the solvent (it does the dissolving).

Even or uneven?

A homogeneous mixture looks the same all the way through — you can't see the separate parts (salt water, air). A heterogeneous mixture is uneven — you can see the different parts (a salad, sand in water).

Quick check, together: Is a bowl of cereal in milk homogeneous or heterogeneous?
Answer: Heterogeneous — you can clearly see the separate pieces of cereal.

What did the beaker teach us?

Mixed, not made — so a mixture can always be separated again.