Lesson 1 of 10
Same all through, or not
Show on a big screenStir salt into water well. Taste from the top, then from the bottom.
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Step 1 of 4
- Two jars, each with a mixture.
- Scoop from the top and the bottom of jar A.
- Scoop from the top and the bottom of jar B.
- A's scoops match. B's scoops do not.
The rule
A mixture is homogeneous when it is the same all through. It is heterogeneous when its parts are not the same everywhere.
A homogeneous mixture is also called a solution. A heterogeneous mixture has parts that differ. Often you can see them. Its parts may settle, or sink to the bottom. Its parts may scatter a beam of light.
| Homogeneous | Heterogeneous |
|---|---|
| Sugar in water | Sand in water |
| Vinegar | Oil and water |
| Soda water | Iron filings and sulfur |
| Brass, an alloy of copper and zinc | Smoke |
| Clean air | Fog |
Gases usually mix evenly, because gas particles move about freely. Two solids stirred together usually stay in patches. Solid pieces do not spread out on their own.
Milk looks even, but its tiny fat drops scatter light. So milk counts as heterogeneous.
Try the lab to finish this lesson.