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.