Why does a block of solid keep its own shape instead of flowing?

1. In a solid the particles are packed closely in a regular arrangement. 2. Strong forces lock each particle into a fixed position. 3. Because the particles cannot change places, the solid keeps a fixed shape. 4. Particles that floated freely apart would describe a gas instead. _Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), The solid state_