What causes a solid have a definite volume and shape?

Answer 1

In a solid, the particles are closely packed together in a regular structure by means of strong forces of attraction. They can only vibrate but cannot move freely. This is why a solid has a definite shape and volume.~

It has definite shape because..

Picture a solid, like a mug, on a table. Is it constantly changing shape? This means that the solid has definite shape. Unless, of course, a steamroller goes over it, but definite shape means with no extra forces.

It has definite volume because..

If you think about it, the amount of space a solid takes up will always be the same, or definite. Even if say, a sponge, was crushed, the volume will be the same. Only the air inside the solid will change.