What is the substance?

Everything created by nature or man-made, there is substance. The table at which you sit, made of wood; the pen with which you write - plastic. Wood and plastic are substances. The ink in the pen, as well as tea in a glass, the clouds in the sky, all this substance.

While the above items are different from each other: table solid, tea, liquid, and cloud and is neither a liquid nor a solid.

In the solid substance molecules are densely pressed to each other, between them there is a strong attraction. In this state they can't freely move, only vibrate. It is so solid it keeps its shape and volume.

Liquid is a state of matter in which molecules feel more free, you can move from place to place. Any liquid takes the shape of the vessel may flow from one vessel to another.

The gaseous substance is a substance in which the particles move freely and randomly. Communication between the gas molecules is very weak, they can be far from each other, filling a large space.