Answer:
1. one particle
2. to represent different states of matter and/or different particles or elements
3. multiple particles or an element with multiple particles
4. the grey bricks would connect to the black one in a triangle shaped way
5. the white bricks would connect with the grey one in the middle with the white ones on both sides of it
extension
1. when you freeze water it becomes ice and vice versa- when you melt it it becomes water
2. it is the same identity either way- ice is only frozen water and when you melt it it will become that once again
I really hope this helps because this was really confusing!