Why sand despite being a solid takes the shape of its container?

Question

The molecules in liquid have enough room to slide over each other so they take the shape of a container. A solid in the other hand has tightly packed molecules. But sand being a solid flows. Why does it take the shape of the container?

Answer 1

Sand "appears" to take the shape of the container, but in actuality it really does not.  There is enough space between the particles of sand, that it will not completely occupy the volume/space of the container.  The reason it appears to do so, and it appears to "flow" like water, is because even though sand is a solid, it is considered to be what is called "granular".  Granular solids are made up of very small solid particles.  The space between these particles is greater than that in a "regular" solid, and this is what allows it to look like it flows and takes the shape of the container.