Final answer:
A thread can change shape because solids, such as metals, are malleable and ductile, meaning they can be reshaped or stretched without breaking. At the molecular level, atoms are held together by forces that can adjust to movement, permitting the change in shape.
Step-by-step explanation:
The question asks how a solid thread, which is seemingly rigid, can change its shape. Materials such as metals are known for their ability to be reshaped without breaking, which is termed as being malleable. Additionally, when a material can be stretched into thin wires, it is described as being ductile. A common example of a ductile and malleable material is copper.
At the molecular level, you can picture solids as consisting of atoms (similar to billiard balls) that are interconnected by forces that act like springs. When external forces are applied, such as stretching or bending, these 'springs' allow the atoms to move around and reposition themselves without breaking the material itself, thereby allowing the thread to change shape.