A little more on solutions and mixtures

Yesterday in class we had a question about solutions–they are not limited to solids dissolved in liquids!  Some alloys are solid solutions, and these are very important to the semiconductor industry.  For example, the solid solution used in an LED can determine the color of light it emits.  If you’re curious and want to learn more, here’s a quick tutorial on solid solutions–you might not have the background to completely understand everything yet, but it’s a nice introduction to some interesting concepts.

Of course, gases can form solutions too.  Without the dissolved oxygen in water, fish would be unable to breathe!  Gases also form homogeneous mixtures with other gases.  My lab has gloveboxes, which rely on a catalyst to keep an inert gas atmosphere inside.  We sometimes have to regenerate the catalyst using a gas that’s composed of 5% hydrogen in nitrogen.




Laws vs. theories

We touched on this a little in class today, and here’s a little more commentary.  Does biology have laws?

I’m glad you noticed that the classification of some of the examples we went through today is context-dependent.  Salt water is a solution, a homogeneous mixture, unless the salt concentration is so high it’s supersaturated…and then, once salt fails to dissolve or precipitates out of solution, we have a heterogeneous mixture.  Smart class!  Too bad I didn’t bring stickers today.

Because we discussed the compressibility of gases today, I feel obligated to show you why compressed gases are dangerous.

All that potential energy can be released pretty quickly if the valve snaps off…and the compressed gas will violently de-compress itself.