What are the 4 states of matter? Any and all substances can exist in one of 4 forms (also called "states" or "phases") Which state the material is in basically depends upon its temperature. The easiest example is water (a liquid). Take away heat and it becomes a solid (we call it ice). Add heat and it turns into a gas we call water vapor. Add more heat and it turns into a high energy form called plasma. In our study of the earth we are most concerned with the first three - plasma becomes more important in astronomy and high energy physics. One of the marvels of water is that it can exist in all 3 states on the surface of the earth - even at the same place and time. Imagine enjoying a glass of ice water on a humid day and tell me you don't believe in magic. One way to understand how the 3 phases differ is to discuss how they relate to being put into something. A solid is rigid with a fixed shape which stays the same no matter what you put it in. Put a rock on the table, into a box, into a backpack - it's still the same rock. A liquid is fluid, and affected by gravity. Therefore, liquids will conform to the shape of whatever they are put into, on earth filling the container from the bottom up. Try pouring a glass of water into a different shaped container and you'll see what I mean. The higher energy of gas pushes gas molecules away from each other, causing a gas to attempt to fill up whatever space is available. That's why a balloon is full, with equal pressure at all locations. By the way, wouldn't balloons be weird if all the gas was at the bottom?