Three of the four are correct. "Liquid" can be a noun or an adjective, but "gas" can't be an adjective. You would have to say, "Steam is gaseous." Since "solid" is countable when it's a noun, you have to use an article or some other determiner before it when it's singular. "Liquid" can be a countable or uncountable noun, so it depends. Of course when they're used as adjectives, whether you need an article (or some other determiner) depends on the noun that they're modifying.

"Solid" is just like "liquid". Ice is solid (adjective) and ice is a solid (noun). "We have two chemicals in the laboratory. One is solid, and the other is liquid. Let's see what happens when we mix some liquid with some solid." This shows how "countability" depends on how you think about the noun. Scientists, for example, often see things differently from the rest of us.