* Mass: the amount of matter in an object.

* Volume: the amount of space an object occupies.

* Density: the mass of an object per unit volume.

If matter collided with non, the following would happen:

* The two objects would exert a force on each other, causing them to accelerate.

* The amount of acceleration would depend on the masses of the two objects and the distance between them.

* If the two objects were moving towards each other, they would collide and bounce off of each other.

* If the two objects were moving away from each other, they would continue to move away from each other.