Determining the state of matter is not easy.  Many times a substance acts like a liquid, but then sometimes it acts as a solid.  Cornstarch and water is a classic example of  this.  If you add the appropriate amount of water to cornstarch it will act as a solid, but then if you let the solid rest, it will flow.  

Matter can also change states of matter depending on the temperature.  Water is an excellent example of how easily you can go from one state to another, just by increasing or decreasing the temperature.

Traditionally we have taught students that there are 3 states of matter.  They assume that this is all there is.   Solids, liquids, and gases are states of matter that are familiar to us on the surface of the Earth.  However, deep in the Earth or deep  in space, conditions are different, allowing other states of matter to dominate.  For instance, plasma is the most common state of matter in the Universe.  

It is important early in a child’s education to make students understand, that humans define parameters within our world.  But that does not make it absolutely correct in other worlds.