Why does an elastic band stretch?
The molecular forces go to a higher energy state when stretched. As the energy state returns to normal, the material snaps back. Some molecules express this higher energy state more forcefully than other materials. Some materials separate (absorb the energy to create the fracture) or dissipate the higher energy as heat, like bending metal. Materials that stretch and return to their original shape demonstrate the property of elasticity. The material’s structure wants to stay that shape, but it can be changed or deformed by applying a countering force. Pulling the material changes the shape and stores energy as the forces counter the tendency for the material to return to a relaxed state. Releasing the material, transforms the energy from potential to kinetic energy as the elastic releases the energy stored in its deformed shape.
