Question

If rubber bands are solid, then how can they stretch?

Answer 1

Hint:Rubber is a kind of natural polymer where chains of molecules have elastic properties. Stretching and deformation of elastic material occur when force is applied on it. This stretching depends on the units of material which it is made of.

Complete step-by-step answer:Rubber can definitely be said as solid, especially an elastic solid which is formed by units of polymeric chains.
Let us discuss further about elasticity and stretching of a rubber band.
Different solids have different kinds of lattice structures. When an external force is applied on the solid, the atoms of the lattice tend to leave their original position, and it leads to deformation of the solid. If this external force is removed, the atoms come back to their original positions (this is due to internal force) and the substance or solid gets restored to its original state. This kind of deformation is known as elastic deformation. But if the internal force is not enough to bring these atoms to their original position, it will lead to the condition of plastic deformation.
Many different substances have different levels of elasticity and plasticity, based on their atom composition and what internal structures they have.
Rubber band is made up of an organic substance called rubber which can be natural as well as synthetic in nature. It is a polymer made up of a very large number of molecular units which may be identical, simple or a bit different, connected repeatedly all together by covalent bonds. This molecular chain or polymer is spirally curved and compressed in different forms. All these chains are cross-linked to each other. When an external force is applied, all the spiral-curved molecules don’t slip past each other but tend to straighten out. And when this external force is removed, it results in coming back to its original shape and size due to the cross-link net inside the rubber. This kind of polymer with elastic properties is known as elastomer. The molecular chains of an elastomer act like springs which can be stretched when force is applied and can come back to their initial state when force is removed after some time.
 Therefore, we may say that even after being a solid, rubber can easily stretch due to its polymeric chains which have elastic properties, and it can be temporarily deformed.

Note:This elastic deformation occurs in a certain range. If we apply a huge amount of external force and if it exceeds the elastic range of the material, then even after the removal of force, the material would not restore to its original structure. It leads to permanent deformation.