Amazingly almost every element can exist as a solid, a liquid, and a gas - it all depends on the temperature. Mercury, for example, is generally found as a liquid but at -40 degrees Celsius it freezes and turns into a solid. And Mercury vapor (gas) is found in some particles of light. Carbon Dioxide (the stuff we breathe out) is generally found as a gas but dry ice (that spooky ice that fogs) is actually carbon dioxide (CO₂) in its solid state. CO₂, however, is interesting as it is one of the few things that do not have a liquid state. Metals (solids) can be melted and turned into a liquid if the heat is high enough. For example, calcium carbonate (the main ingredient in limestone) has a melting point of 1339 degrees Celsius - now that's hot! And liquids can be boiled and turned into a gas if the heat is again at a certain point that varies by substance. Potassium, for example, has a melting point of 63.5 degrees Celsius at which point it turns from a solid into a liquid, and it has a boiling point of 759 degrees Celsius at which point it turns from a liquid into a gas.

It turns out that nearly everything can exist in 3 states; it is just a question of finding the right temperatures. For instance, oxygen, a gas, becomes a liquid if you cool it down to - 297 degrees Fahrenheit (really, REALLY cold) and if you cool it down further to -362 degrees Fahrenheit it becomes a solid. Iron, a solid at room temperature, becomes a liquid at 2800 degrees Fahrenheit (really, REALLY hot) and a gas at 5182 degrees Fahrenheit (about half the temperature of the sun).

When things are hot, the molecules and atoms move around more and faster, and when they are cold they are slower. The temperature you need to make the molecules move fast enough to be a gas or slow enough to be a solid depends on the type of interactions between the molecules.

Every element can exist in all three states.

Nearly everything that you are familiar with can exist as a solid, a liquid, or a gas. There is a fourth phase, too, plasma, that things can exist as.

Everything can exist in all 3 states, depending on the temperature and pressure. For example, even the air (mostly nitrogen) will turn into a liquid if it becomes cold enough. Water just happens to be close to the temperature region that we live in, and it's all around us, so we notice it more than other things.