Mixtures Keep Their Properties

Today you will learn how to show and explain that the parts of some mixtures keep their own physical properties.

A mixture is two or more substances that are put together but do not change into something new. Think about a bowl of trail mix. You can still see the peanuts, the raisins, and the pretzels. Each one keeps its own color, shape, and taste. If you do not like raisins, you can pick them out with your fingers. That works because each part stayed the same.

A physical property is something you can observe or measure, like color, size, shape, or whether something floats or is attracted to a magnet. In a mixture, these properties stay with each substance. Sand is still rough and tan. Iron filings are still gray and still stick to a magnet. When you stir sand and iron filings together, neither one changes. Hold a magnet over the pile, and the iron filings jump up to it. The sand stays behind. That is proof that both kept their properties.

Sand and water work the same way. Pour sand into a cup of water and stir it hard. The water is still a clear liquid, and the sand is still tiny solid grains. Wait a few minutes, and the sand sinks to the bottom because it is heavier than the water and does not dissolve. You could pour the water off, dry the sand in the sun, and have your sand back just like before.

This is different from mixing cake batter and baking it. Baking makes a new substance you cannot separate. In the mixtures we studied, nothing new is made, so you can always pull the parts apart again.

Try it: If you mixed paper clips with dry rice, what tool could you use to pull out only the paper clips, and why would it work?